WO2014160333A1

WO2014160333A1 - Methods for preparation of polyester via base catalysis

Info

Publication number: WO2014160333A1
Application number: PCT/US2014/026337
Authority: WO
Inventors: Jimmy Lynn Webb; III John LIPPERT; James MIHALICH
Original assignee: Liquid Thermo Plastics, Inc.
Priority date: 2013-03-13
Filing date: 2014-03-13
Publication date: 2014-10-02

Abstract

Presented herein are methods and systems for preparing polyester, e.g., polybutylene terephthalate (PBT), using a base catalyst, e.g., a heterocyclic amine such as triazabicyclodecene (TBD). It is found that such base catalysts are effective in the production of polyester, and they reduce the potential for undesired byproducts such as furans (e.g., THF) and acetaldehyde (AA), which result from diol side reactions.

Description

METHODS FOR PREPARATION OF POLYESTER

VIA BASE CATALYSIS

Cross Reference to Related Applications

[001] The present application claims priority to U.S. provisional patent application number 61/780,591, filed March 13, 2013, and U.S. provisional patent application number 61/940,401, filed February 15, 2014, the entire contents of each of which are hereby incorporated by reference herein.

Field of the Invention

[002] This invention relates generally to methods for preparing polyesters such as polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). More particularly, in certain embodiments, the invention relates to methods for preparing polyesters using a base catalyst.

Background of the Invention

[003] Polyesters makes up nearly one-fifth of the world polymer production.

Polyethylene terephthalate (PET) is a popular polyester which is widely used in consumer goods, for example "polyester" textiles. Its good gas and moisture barrier properties, high mechanical strength, and impact-resistance make it an ideal material for synthetic fibers, food and beverage containers, and engineering resins. [004] Polybutylene terephthalate (PBT) is a high performance polyester that displays excellent mechanical and electrical properties, and possesses robust chemical resistance. PBT lends valuable characteristics to polymer products, for example, high dimensional stability, low moisture absorption, and powerful insulation resistance, and is used in various applications including automotive, electrical, industrial, and consumer goods. The global market for PBT is sizable and estimated to reach 1.3 million tons by 2017.

[005] PBT is conventionally produced by combining a terephthalic acid alkyl ester comprising dimethyl terephthalate with a glycol comprising 1,4-butanediol. The mixture is contacted with a metal-containing transesterification catalyst, such as a titanium, halfnium, or lanthanum catalyst, to form bis-hydroxybutyl terephthalate, as well as methanol and THF as by-products. Following transesterification, the reaction product undergoes pre-polycondensation, either in a separate reactor or in the same reactor that transesterification takes place (e.g., the Zimmer COMBI reactor and the Uhdelnventa- Fischer ESPREE and DISCAGE reactors combine esterification and pre- polycondensation in one reactor). Pre -polymerization may make use of an additional catalyst or the same catalyst as transesterification. The product then undergoes polymerization in a separate polycondensation reactor under high vacuum to build high molecular weight.

[006] PET is made in a similar fashion, except that ethylene glycol is substituted for butylene glycol.

[007] Due to the global demand for polyesters and the difficulty in avoiding byproducts, there remains a need for improved methods of manufacturing polyesters. Summary of the Invention

[008] Presented herein are methods and systems for preparing polyester, e.g., polybutylene terephthalate (PBT), polypropylene terephthalate (PPT),

polycyclohexylenedimethylene terephthalate (PCT), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN), using a base catalyst, e.g., a heterocyclic amine such as triazabicyclodecene (TBD). It is found that such base catalysts are effective in the production of polyester, and they reduce the potential for undesired byproducts such as furans (e.g., THF) and acetaldehyde (AA), which result from diol side reactions.

[009] Metal alkoxides such as sodium methoxide and potassium methoxide are also found to perform as effective base catalysts in the production of polyester. The potential for production of THF from diol side reactions is reduced in comparison to the use of acidic or neutral catalysts such as organo-titanates, for example. Furthermore, organic bases, particularly heterocyclic amines such as triazabicyclodecene (TBD), are found to be efficient catalysts. Lower amounts of catalyst are needed, and the potential for furan or acetaldehyde production is low.

[0010] Moreover, it has been found that use of a phenol di-ester such as diphenyl terephthalate (DPT) in the transesterification eliminates or reduces methano lysis. For example, an initial stage for preparation of polyester involves reacting terephthalic acid and phenol in an esterification reactor to produce DPT, which is fed into a

transesterification reactor in which a base-catalyzed reaction as described herein takes place. Phenol is evolved and fed back into the esterification reactor.

[0011] For example, current PET and PBT process technology involves a two-step process prior to polycondensation - one step to make an acid, and another step to make an ester, similar to embodiments described herein. However, current processes use an acid catalyst, and a diol with the same alkyl group that becomes part of the polymer (e.g., use of BDO for preparation of PBT). Without wishing to be bound to a particular theory, the diol used in current processes cyclizes to THF and acetaldehyde via the acidic catalyst, and the transesterification reaction is inefficient. The initial esterification in current processes is run with an excess of diol, and high vacuum is required to pull diol out as soon it is formed, before it reacts to form THF/AA byproducts.

[0012] In contrast, by using a base catalyst and a phenol di-ester such as diphenyl terephthalate (DPT), the transesterification runs much more efficiently because it appears that the phenol group is more easily replaced (without wishing to be bound by any particular theory), and there is no (or greatly reduced) THF/AA byproduct produced. Use of phenol allows the reaction to proceed more rapidly than use of a methyl, ethyl, or butyl end group, for example.

[0013] The experiments described herein were conducted for preparation of

macrocyclic polyester oligomer (MPO) using base catalysts, but these experiments also demonstrate that the full polyester may be created using these base catalysts, e.g., by running the same transesterification reactions described in the experiments without added solvent. The transesterification product can be further processed, e.g., in a

polycondensation reactor, for increasing molecular weight.

[0014] In one aspect of the invention, polyester is prepared by heating a reaction mixture comprising (i) an alcohol, phenol, or both; (ii) a terephthalate di-ester (e.g., DPT); and (iii) a base catalyst (e.g., an organic base), to form a polyester. In some embodiments, the reaction mixture comprises a substituted or unsubstituted aromatic alcohol (e.g., a substituted phenol such as cresol). In some embodiments, no catalyst is used other than the base catalyst. In some embodiments, the terephthalate di-ester is a phenol di-ester. In some embodiments, the phenol di-ester is DPT. In some embodiments, the terephthalate di-ester is DMT.

[0015] Features described with respect to other aspects of the invention can be applied to this aspect as well.

[0016] In another aspect, polyester is prepared by a process comprising (a) contacting terephthalic acid (TPA) and a single functional alcohol in an esterification reactor to produce a di-ester (e.g., DPT); and (b) contacting the di-ester with a diol and a base catalyst in a trans-esterification reactor, to form a polyester. In some embodiments, a single function alcohol is an aromatic alcohol. In some embodiments, a single functional aromatic alcohol is phenol. In some embodiments, a di-ester is diphenyl terephthalate (DPT). In some embodiments, a di-ester is dialkyl terephthalate. In some embodiments, a di-ester is dimethyl terephthalate (DMT). In some embodiments, a polymer is a copolymer. In certain embodiments, no catalyst is used in the trans-esterification reactor other than the base (e.g., the trans-esterification reaction is base-mediated). In some embodiments, step (a) comprises heating a melt blend comprising at least one of (i) terephthalic acid and isophthalic acid, and at least one of (ii) hydroquinone and resorcinol.

[0017] Features described with respect to other aspects of the invention can be applied to this aspect as well. [0018] In some embodiments, a process described herein further comprises performing a polycondensation reaction with polyester formed in a trans-esterification reactor, thereby increasing molecular weight of the polyester.

[0019] In some embodiments of the methods and processes described herein, the base is an organic base. In some embodiments, the base is an amine base (e.g.,

triazabicyclodecene (TBD)). In other embodiments, the base is or comprises one or both of sodium alkoxide (e.g., sodium methoxide) and potassium alkoxide (e.g., potassium methoxide).

[0020] In some embodiments of the methods and processes described herein, reaction mixtures used in accordance with the invention comprise a diol. Suitable diols include but are not limited to: polyethylene glycol, polypropylene glycol, 1 ,2-ethanediol, 1,2- propanediol, 1,3 -propanediol, 1 ,2-butanediol, 1,3-butanediol, 1 ,4-butanediol, 1,5- pentanediol, 2,2-dimethylpropane-l,3-diol, 2-butyl-2-ethylpropane-l,3-diol, 1,5- hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 2,2,4,4- tetramethylcyclobutane-l,3-diol, 1,3-cyclopentanediol, 1 ,2-cyclohexanediol, 1,3- cyclohexanediol, 1 ,4- cyclohexanediol, 1 ,2-cyclohexanedimethanol, 1,3- cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol, and 1 ,4-cyclohexanediethanol. In some embodiments, the diol is polyethylene glycol. In some embodiments, the diol is butanediol. In some embodiments, the diol is 1,4-butanediol.

[0021] In some embodiments, reaction mixtures used in accordance with the invention comprise a phenol (e.g., resorcinol or hydroquinone).

[0022] In some embodiments of the methods and processes described herein, the content of the esterification reactor is maintained at a temperature of at least 180 °C (e.g., about 300 °C). In some embodiments, the content of the trans-esterification reactor is maintained at a temperature of between about 230 °C and about 260 °C.

[0023] In some embodiments of the methods and processes described herein, the base catalyst does not contain a metal.

Brief Description of the Drawings

[0024] The objects and features of the invention can be better understood with reference to the drawings described below, and the claims. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views.

[0025] Figure 1 is a flow diagram illustrating a process for preparing MPO according to an illustrative embodiment of the invention.

[0026] Figure 2 is a flow diagram illustrating a process for preparing PBT (or other polyester) according to an illustrative embodiment of the invention.

Description of Certain Embodiments

[0027] Throughout the description, where compositions, mixtures, blends, and composites are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are compositions, mixtures, blends, and composites of the present invention that consist essentially of, or consist of, the recited components, and that there are processes and methods of the present invention that consist essentially of, or consist of, the recited processing steps. [0028] It should be understood that the order of steps or order for performing certain actions is immaterial so long as the invention remains operable. Moreover, two or more steps or actions may be conducted simultaneously.

[0029] Macrocyclic polyester oligomers that may be employed in this invention include, but are not limited to, macrocyclic poly(alkylene dicarboxylate) oligomers having a structural repeat unit of the formula:

O O O A O C B C

where A is an alkylene, or a cycloalkylene or a mono- or polyoxyalkylene group; and B is a divalent aromatic or alicyclic group.

[0030] Preferred macrocyclic polyester oligomers include macrocyclic poly(l ,4- butylene terephthalate) (cPBT), macrocyclic poly( 1,3 -propylene terephthalate) (cPPT), macrocyclic poly(l,4-cyclohexylenedimethylene terephthalate) (cPCT), macrocyclic poly(ethylene terephthalate) (cPET), macrocyclic poly(l,2-ethylene 2,6- naphthalenedicarboxylate) (cPEN) oligomers, and copolyester oligomers comprising two or more of the above monomer repeat units.

[0031] Methods of the invention may be used to produce macrocyclic homo- and copolyester oligomers. In one embodiment, macrocyclic ester homo- and co-oligomers produced via methods of this invention include oligomers having a general structural repeat unit of the formula:

O

I I

O— A'— C where A' is an alkylene, cycloalkylene, or mono- or polyoxyalkylene group, and where A' may be substituted, unsubstituted, branched, and/or linear. Example MPOs of this type include butyrolactone and caprolactone, where the degree of polymerization is one, and 2, 5-dioxo-l,4-dioxane, and lactide, where degree of polymerization is two. The degree of polymerization may also be 3, 4, 5, or higher. Molecular structures of 2, 5- dioxo-l,4-dioxane and lactide, respectively, appear below:

[0032] In general, a macrocyclic polyester oligomer (an MPO) produced via methods described herein includes species of different degrees of polymerization, although, in certain embodiments, MPO with a high concentration of a particular species may be produced. Here, a degree of polymerization (DP) with respect to the MPO means the number of identifiable structural repeat units in the oligomeric backbone. The structural repeat units may have the same or different molecular structure. For example, an MPO may include dimer, trimer, tetramer, pentamer, and/or other species. In certain embodiments, the MPO is primarily (e.g., consists essentially of) dimer, trimer, tetramer, and/or pentamer species. In certain embodiments, the MPO is primarily (e.g., consists essentially of) trimer, tetramer, and/or pentamer species (e.g., C3+C4+C5).

[0033] Where methods of the invention refer to the use of a dialkyl terephthalate, such as DMT, those methods are also contemplated to include variations of the method in which terephthalic acid (TP A) is used instead of at least a portion of the dialkyl terephthalate. For example, it is contemplated that a method of the invention in which a reaction is performed using a dialkyl terephthalate and a diol inherently includes an adaptation in which terephthalic acid is used instead of (or in addition to) dialkyl terephthalate. For example, known methods for the conversion of TP A to DMT may be used. Similarly, the use of known chemical analogues and/or precursors of species described herein are considered to lie within the scope of the claimed subject matter.

[0034] It is contemplated that methods, systems, and processes of the claimed invention encompass scale-ups, variations, and adaptations developed using information from the embodiments described herein. For example, the invention includes pilot plant and plant- scale manufacturing processes whose feasibility is demonstrated by the laboratory-scale experiments described herein. The chemical reactions described herein may be performed using reactor equipment that is known to those of ordinary skill in the field of polymer manufacturing and processing, including, without limitation, for example, batch reactors, plug-flow reactors, continuously-stirred tank reactors, packed-bed reactors, slurry reactors, fluidized bed reactors, and columns. Chemical reactions described herein may be conducted in batch, semi-continuous, and/or continuous operation.

[0035] Scale-up of systems from laboratory to plant scale may be performed by those of ordinary skill in the field of polymer manufacturing and processing. For example, those of ordinary skill in this field may select reactor types, design experiments for obtaining kinetic data, develop and apply models for reactor design, develop

economically optimum reactor design, and/or validate reactor designs via pilot plant and/or full scale reactor experiments. General information regarding reactors and the design of reactor systems for manufacture of products may be found, for example, in "Kinetics and Reaction Engineering," John L. Falconer, editor, in The Engineering Handbook, Section X, Richard C. Dorf, editor-in-chief, CRC Press, Inc.,

ISBN 0-8493-8344-7, pp. 785-829 (1995).

[0036] Any suitable techniques for material separation, isolation, and purification may be adapted for application in manufacturing processes encompassed by various embodiments of the invention, for example, techniques for distillation, extraction, reactive extraction, adsorption, absorption, stripping, crystallization, evaporation, sublimation, diffusional separation, adsorptive bubble separation, membrane separation, and/or fluid-particle separation. General information regarding separation processes and their design may be found, for example, in "Separation Processes," Klaus Timmerhaus, editor, in The Engineering Handbook, Section VIII, Richard C. Dorf, editor-in-chief, CRC Press, Inc., ISBN 0-8493-8344-7, pp. 579-657 (1995).

[0037] It is also contemplated that methods, systems, and processes of the claimed invention may include pumps, heat exchangers, and gas-, liquid-, and/or solid-phase material handling equipment known to those of ordinary skill in the field of polymer manufacturing and processing.

[0038] Embodiments of the invention may be performed as part of a continuous, semi- continuous, or batch process. Reactors may be single-stage or multi-stage. It is contemplated that methods of the invention may be combined or supplemented with reactors, systems, or processes that are known in the art.

[0039] The mention herein of any publication, for example, in the Background section, is not an admission that the publication serves as prior art with respect to any of the claims presented herein. The Background section is presented for purposes of clarity and is not meant as a description of prior art with respect to any claim.

[0040] As used herein, "macrocyclic" is understood to mean a cyclic molecule having at least one ring within its molecular structure that contains 5 or more atoms covalently connected to form the ring.

[0041] As used herein, an "oligomer" is understood to mean a molecule that contains one or more identifiable structural repeat units of the same or different formula.

[0042] As used herein, "macrocyclic polyester oligomer" (MPO), or "cyclics", is understood to mean macrocyclic oligomer containing structural repeat units having an ester functionality. A macrocyclic polyester oligomer typically refers to multiple molecules of one specific repeat unit formula. However, a macrocyclic polyester oligomer also may include multiple molecules of different or mixed formulae having varying numbers of the same or different structural repeat units. Thus, the terms "macrocyclic polyester oligomer" and "macrocyclic polyester oligomers" (plural form) may be used interchangeably. Also, the terms "macrocyclic polyester oligomer" and "macrocyclic oligoester" are used interchangeably herein. A macrocyclic polyester oligomer may be a co-polyester or multi-component polyester oligomer, i.e., an oligomer having two or more different structural repeat units having ester functionality within one cyclic molecule.

[0043] As used herein, the term "phenol di-ester" refers to a terephthalate where both carboxyl groups are ester groups, and wherein each ester group comprises a carboxyl oxygen bonded to a phenyl group. [0044] As used herein, "substantially homo- or co-polyester oligomer" is understood to mean a polyester oligomer wherein the structural repeat units are substantially identical or substantially composed of two or more different structural repeat units, respectively. Unless otherwise noted, the polyester oligomers described herein include substantially homo-polyester oligomers as well as substantially co-polyester oligomers.

[0045] As used herein the term "terephthalate di-ester" refers to a terephthalate where both carboxyl groups are ester groups.

[0046] Various organic solvents may be used to practice certain embodiments described herein. In some embodiments, the organic solvent is a high-purity hydrocarbon solvent, for example, such as Drakesol 165, manufactured by Orica Chemicals, which is composed of acid-treated light petroleum distillates. Other similar solvents may be used, as well. In some embodiments, the organic solvent may include at least one member selected from the group consisting of dibutyl ether, decane, dodecane, tetradecane, hexadecane, octadecane, heptane, toluene, xylene, trimethylbenzene, tetramethylbenzene, ethylbenzene, propylbenzene, naphthalene, methylnaphthalene, biphenyl, triphenyl, diphenyl ether (or a halogenated derivative thereof), anisol, pyridine, triethylamine, methylene chloride, dimethyoxybenzene, chlorobenzene, dichlorobenzene,

trichlorobenzene, chloronaphthalene, dichloronaphthalene, and/or a perfluorocarbon. In particular embodiments, the organic solvent may include oDCB, toluene, o-xylene, pyridine, triethylamine, heptane, dibutyl ether, decane, dodecane, or trichlorobenzene (TCB). In some embodiments, the organic solvent may include toluene.

[0047] Base catalysts that may be used to practice certain embodiments described herein include known organic, inorganic bases, and combinations thereof. In certain embodiments, the base catalyst is an organic base. In some embodiments, the base catalyst is not a metal-containing compound. In some embodiments, the catalyst is an amine. In some embodiments, the base catalyst is a tertiary amine. In some

embodiments, a catalyst is a trialkylamine, dialkylamine, or partially unsaturated or aromatic heterocyclic amine. In some embodiments, the base catalyst is triethylamine, DIPEA, N-methyl morpholine, DABCO, diisopropylamine, DBU, DMAP, PPTS, triazabicyclodecene (TBD), or imidazole. In some embodiments, the base catalyst is TBD.

[0048] In some embodiments, a base catalyst is a metal alkoxides or carbonate. In some embodiments, a base catalyst is sodium bicarbonate, sodium carbonate, or potassium carbonate. In some embodiments, a base catalyst is a sodium or potassium alkoxide. In some embodiments, a base catalyst is sodium methoxide. In other embodiments, a base catalyst is potassium methoxide.

[0049] Figure 1 is a schematic diagram of a process 100 for preparing MPO according to an illustrative embodiment. Certain embodiments involve methods and processes for performing the trans-esterification reaction of the reactor 104. Other embodiments involve methods and processes for performing an initial esterification reaction 102 to produce a product (e.g., a di-ester such as DPT) that is fed into the trans-esterification reactor 104. Other embodiments additionally involve performing a separation of MPO from a product stream, e.g., by running the product through a first heat exchanger 106, through a hot filter 108, through a second heat exchanger 110, and/or through a cold filter 112, after which the remaining MPO product is sent for purification, pelletization, and/or packaging. [0050] In one example, terephthalic acid and phenol are fed into the esterification reactor 102, which takes place at a temperature from about 180 °C to about 300 °C. The reaction produces H₂0, which is released. At least a portion of the phenol fed into the esterification reactor 102 may be the phenol that is produced in the trans-esterification reactor 104 and recycled into the esterification reactor 102. The product of the esterification reactor 102 in this example is diphenyl terephthalate (DPT).

[0051] The DPT produced in the esterification reactor 102 is fed into the trans- esterification reactor 104, along with butanediol, base catalyst, and solvent, examples of which are described herein. The reaction mixture is maintained at a temperature from about 230 °C to about 260 °C in the trans-esterification reactor. One example of a base catalyst that is found to work particularly well is TBD. The phenol is more easily replaced as an end group by the diol and has a favorable equilibrium with the desired diol. Use of phenol makes the reaction much faster than use of a methyl, ethyl, or butyl end group, for example. The base catalyst does not react with the diol, so no THF or acetaldehyde is formed. The reaction is run at low solids concentration (e.g., at a concentration no greater than about 5 wt.%, no greater than about 4 wt.%, no greater than about 3 wt.%, no greater than about 2 wt.%, or no greater than about 1 wt.%). The evolved phenol is redirected back into the esterification reactor 102, while a product stream proceeds into the first heat exchanger 106.

[0052] Separation of MPO from the reaction mixture leaving the trans-esterification reactor is performed by reducing the temperature of the reaction mixture. The reaction mixture is maintained within a temperature range in which the polyester linears that are produced substantially precipitate out of the reaction mixture (e.g., at least about 80 wt.% of the polyester linears in solution precipitate out), but in which the MPO substantially does not precipitate out of the reaction mixture (e.g., at least about 80 wt.% of the MPO in solution stays in solution). A substantial portion of the base catalyst associates with (e.g., adsorbs to, binds to, or attaches to) the polyester linears, so a substantial portion of the base catalyst (e.g., at least about 95 wt.%, at least about 98 wt.%, at least about 99 wt.%), at least about 99.5 wt.%, or at least about 99.9 wt.%) can be removed from the reaction mixture by precipitation. In the process 100 of Figure 1, the recovered catalyst and/or recovered polyester linears may be recycled back into the trans-esterification reactor 104.

[0053] In certain embodiments, the first heat exchanger 106 takes the product reaction mixture from about 240 °C down to a temperature from about 120 °C to about 180 °C. The product enters the hot filter 108, and the MPO-containing mixture proceeds to the second heat exchanger 110 while another portion is recycled to the first heat exchanger 106. The second heat exchanger 110 takes the feed down to a lower temperature, for example, from a temperature from 120 °C - 180 °C to a temperature 40 °C - 100 °C, after which the product enters the cold filter 112. A portion of the mixture containing MPO is removed from the cold filter 112 for purification, pelletization, and packaging, while another portion of the mixture is fed back into the second heat exchanger 110.

[0054] Figure 2 is a schematic diagram of a process 200 for preparing PBT (or other polyester) according to illustrative embodiments of the invention. Certain embodiments of the invention involve methods and processes for performing the trans-esterification reaction of the reactor 204. Other embodiments involve methods and processes for performing an initial esterification reaction 202 to produce a product (e.g., a di-ester such as DPT) that is then fed into the trans-esterification reactor 204. Other embodiments additionally include performing polycondensation in the polycondensation reactor 206 to increase the molecular weight of the ester prepared in the trans-esterification reactor 204. Other embodiments additionally involve performing purification of the product, solids handling, and/or packaging.

[0055] Although Figure 2 depicts the unit operations as separate reactors, it should be noted that combinations of two or more of (i) esterification, (ii) trans-esterification, and/or (iii) pre -polycondensation may be performed in a single reactor vessel (e.g., using reactors such as the Zimmer COMBI reactor or the Uhdelnventa-Fischer ESPREE or DISCAGE reactor).

[0056] In one example, terephthalic acid and phenol are fed into the esterification reactor 202 of Figure 2, which takes place at a temperature from about 180 °C to about 300 °C. The reaction produces H₂0, which is released. At least a portion of the phenol fed into the esterification reactor 202 may be the phenol that is produced in the trans- esterification reactor 204 and recycled into the esterification reactor 202. The product of the esterification reactor 202 in this example is diphenyl terephthalate (DPT).

[0057] The DPT produced in the esterification reactor 202 is fed into the trans- esterification reactor 204, along with butanediol, and a base catalyst, examples of which are described herein. The reaction mixture is maintained at a temperature from about 230 °C to about 260 °C in the trans-esterification reactor. One example of a base catalyst is triazabicyclodecene (TBD). The phenol is more easily replaced as an end group by the diol and has a favorable equilibrium with the desired diol. Use of phenol makes the reaction much faster than use of a methyl, ethyl, or butyl end group, for example. The base catalyst does not react with the diol, so no THF or acetaldehyde is formed. In preferred embodiments, the reaction is run at high solids concentration (e.g., 100 wt.%), and no added solvent is necessary. The evolved phenol is redirected back into the esterification reactor 202, while a product stream proceeds into the polycondensation reactor 206. In the process 200 of Figure 2, the recovered catalyst may be recycled back into the trans-esterification reactor 204. Polyester molecular weight is increased in the polycondensation reactor 206, which is run under vacuum.

Experimental Examples

General Experimental Procedure for the Synthesis of MPO

[0058] To a mixture of 1 ,4-butanediol (BDO) in solvent at a given temperature was added catalyst. DMT or DPT was then added to the mixture and the reaction maintained at the specified temperature. High pressure liquid chromatography analysis after a designated time showed that a mixture of cyclics were obtained, and area calculated. Results for specific experiments are shown in Table 1. DMT = dimethyl terephthalate; DPT = diphenyl terephthalate; TBD = l,5,7-triazabicyclo(4.4.0)dec-5-ene; DBU = 1,8- Diazabicyclo[5.4.0]undec-7-ene.

Constructive Experimental Example for the Synthesis of PBT

[0059] Terephthalic acid and phenol are combined in an esterification reactor to produce DPT. The DPT produced in the esterification reactor is fed into a trans- esterification reactor, along with butanediol and a base catalyst. In order to increase the molecular weight of the polymer, the polymerization process then continues in a polycondensation reactor, from which PBT product is isolated and purified.

Table 1 - Experiments run for synthesis of MPO

-20-

6072922vl

* The integration % includes all byproducts and intermediates based on HPLC results

-21-

6072922vl

Equivalents

[0060] While the invention has been particularly shown and described with reference to specific preferred embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

CLAIMS What is claimed is:

1. A method for preparing a polyester via base-mediated organic reaction, the method comprising heating a reaction mixture, the reaction mixture comprising:

(i) an alcohol, phenol, or both;

(ii) a terephthalate di-ester; and

(iii) a base catalyst (e.g., an organic base), thereby forming a polyester.

2. The method of claim 1, wherein the reaction mixture comprises a substituted or unsubstituted aromatic alcohol (e.g., a substituted phenol such as cresol).

3. The method of claim 1 or 2, wherein no catalyst is used other than the base catalyst.

4. The method of any one of the preceding claims, wherein the base is an organic base.

5. The method of claim 4, wherein the base is or comprises triazabicyclodecene (TBD).

6. The method of any one of claims 1-3, wherein the base is or comprises one or both of sodium alkoxide (e.g., sodium methoxide) and potassium alkoxide (e.g., potassium methoxide).

7. The method of any one of claims 1-6, wherein the reaction mixture comprises a diol.

8. The method of claim 7, wherein the diol is butanediol.

9. The method of any one of claims 1-6, wherein the reaction mixture comprises a phenol.

10. The method of claim 9, wherein the phenol is resorcinol.

11. The method of claim 9, wherein the phenol is hydroquinone.

12. The method of any one of the preceding claims, wherein the polyester is polybutylene terephthalate.

13. The method of any one of the preceding claims, wherein the terephthalate di-ester is a phenol di-ester.

14. The method of claim 13, wherein the phenol di-ester is DPT.

15. The method of any one of claims 1-12, wherein the terephthalate di-ester is DMT.

16. The method of any one of the preceding claims, wherein the polyester is a member selected from the group consisting of PBT, PPT, PCT, PET, and PEN.

17. A process for preparing polyester via base-mediated organic reaction, the process comprising:

(a) contacting terephthalic acid (TP A) and a single functional alcohol in an esterification reactor to produce a di-ester; and

(b) contacting the di-ester with a diol and a base catalyst in a trans- esterification reactor, thereby forming polyester.

18. The process of claim 17, wherein the single functional alcohol is an aromatic alcohol.

19. The process of claim 18, wherein the single functional aromatic alcohol is phenol and the di-ester is diphenyl terephthalate (DPT).

20. The process of claim 17, wherein the di-ester is dialkyl terephthalate.

21. The process of claim 20, wherein the di-ester is dimethyl terephthalate (DMT).

22. The process of any one of claims 17-21, wherein the diol is butanediol.

23. The process of any one of claims 17-22, wherein the base catalyst is or comprises triazabicyclodecene (TBD).

24. The process of any one of claims 17-23, wherein the base catalyst is or comprises one or both of sodium alkoxide (e.g., sodium methoxide) and potassium alkoxide (e.g., potassium methoxide).

25. The process of any one of claims 17-24, wherein the polymer is poly(butylene terephthalate) (PBT).

26. The process of any one of claims 17-24, wherein the polymer is a member selected from the group consisting of PBT, PPT, PCT, PET, and PEN.

27. The process of any one of claims 17-26, wherein the polymer is a copolymer.

28. The process of any one of claims 17-27, wherein no catalyst is used in the trans- esterification reactor other than the base (e.g., the trans-esterification reaction is base- mediated).

29. The process of any one of claims 17-28, further comprising performing a polycondensation reaction with polyester formed in a trans-esterification reactor, thereby increasing molecular weight of the polyester.

30. The process of any one of claims 17-29, wherein step (a) comprises heating a melt blend comprising at least one of (i) terephthalic acid and isophthalic acid, and at least one of (ii) hydroquinone and resorcinol.

31. The process of any one of claims 17-30, wherein the content of the esterification reactor is maintained at a temperature of at least 180 °C (e.g., about 300 °C).

32. The process of any one of claims 17-31 , wherein the content of the trans- esterification reactor is maintained at a temperature of between about 230 °C and about 260 °C.

33. The method of any one of claims 1-16, wherein the base catalyst does not contain a metal.

34. The process of any one of claims 17-32, wherein the base catalyst does not contain a metal.