Bis(glycol) terephthalates and methods for preparing polyester resins using same

Abstract

By a transesterification reaction in which a predetermined amount of bis(2-hydroxyethyl) terephthalate is fed in portions or continuously to glycol, bis(glycol) terephthalates with low amounts of ethylene glycol derivative residues can be prepared, from which polyester engineering products or biodegradable polyester products with high crystallinity can be produced.

Description

[Technical field]

[0001] The present invention relates to the preparation of bis(glycol) terephthalates using recycled monomers, and to polyester resins and articles obtained therefrom. [Background technology]

[0002] Due to its excellent mechanical strength, heat resistance, transparency, and gas barrier properties, polyester is widely used as a material for beverage containers, packaging films, audio and video films, etc. In addition, polyester is widely produced worldwide as an industrial material for medical fibers, tire cords, etc. In particular, polyester sheets or plates have good transparency and excellent mechanical strength, so they are widely used as raw materials for cases, boxes, partitions, shelves, panels, packaging materials, building materials, interior materials, and exterior materials, etc.

[0003] As a result, plastic waste such as polyester is generated at an uncontrollable level worldwide every year. In recent years, countries around the world have been creating regulations and systems for recycling waste plastic resources, including waste polyester. Physical or chemical methods are used to recycle waste polyester, but physical recycling methods cannot guarantee purity and are not widely used.

[0004] In chemical recycling, the ester bonds of waste polyester are broken and depolymerized. Reactions such as glycolysis, hydrolysis, methanolysis, and aminolysis are used. Among them, glycolysis is the decomposition of waste polyester by adding glycols such as ethylene glycol or diethylene glycol at high temperature. For example, bis(2-hydroxyethyl) terephthalate (BHET) can be obtained by glycolysis of waste polyethylene terephthalate (PET), and it is known to use it as a raw material to prepare polyester resin.

[0005] However, from the viewpoint of environmental consideration, it is more meaningful to convert waste PET products, which generally have a short life span, into engineering polyester products, which have a long life span, or into environmentally friendly biodegradable polyester products. In this regard, in recent years, attempts have been made to regenerate polyester resins other than PET by transesterification of waste PET and glycol. In this reaction, an excessive amount of glycol is used and the reaction time is long, so there is a problem that a large amount of by-products such as cyclic ester compounds are formed as a side reaction of glycol. [Prior art document]

[0006] (Non-Patent Document 1) Park, SH, Kim, SH, Poly(ethylene terephthalate) recycling for high value added textiles, Fashion and Textiles 1, 1 (2014) Summary of the Invention [Problem to be solved by the invention]

[0007] Technical Problem The inventors attempted to develop a technology for recycling BHET obtained by depolymerization of waste PET-based products into various engineering polyester products or environmentally friendly biodegradable polyester products, which would allow minimizing the formation of by-products without using excessive amounts of glycols.

[0008] On the one hand, recycled BHET generally has low purity due to impurities formed from the reagents used in the depolymerization process and side reactions, so costly processes such as ion exchange or recrystallization are required to purify it, making it difficult to utilize commercially.

[0009] As a result of research to solve this problem, it has become possible to obtain high-purity bis(glycol) terephthalate while using low-purity BHET or reducing the amount of glycol used by feeding BHET in portions or continuously to the transesterification reaction with various glycols. As a result, it has become possible to produce various high-quality engineering polyester products or environmentally friendly biodegradable polyester products.

[0010] Therefore, the objective of the present invention is to prepare high purity bis(glycol) terephthalate by using recycled BHET without using excess amount of glycol, and to provide various polyester resins and high quality articles therefrom. [Means for solving the problem]

[0011] According to an embodiment of the present invention, the process includes the steps of (1) supplying at least one glycol component having 3 or more carbon atoms to a reaction vessel, and (2) supplying bis(2-hydroxyethyl) terephthalate to the reaction vessel in portions or continuously to carry out an ester exchange reaction, and the ester exchange reaction satisfies the following relationship formula (1): 0≦G / B≦3.5...(1) A method for preparing a bis(glycol) terephthalate is provided, in which:

[0012] In formula (1), G is the total number of moles of at least one glycol component, and B is the total number of moles of bis(2-hydroxyethyl) terephthalate.

[0013] According to another aspect of the present invention, there is provided a method for preparing a polyester resin, comprising the steps of: (1) supplying at least one glycol component having 3 or more carbon atoms to a reaction vessel; (2) supplying bis(2-hydroxyethyl) terephthalate to the reaction vessel in portions or continuously to carry out an ester exchange reaction; and (3) subjecting the product of the ester exchange reaction to a polycondensation reaction, wherein the above-mentioned relationship formula (1) is satisfied.

[0014] According to another aspect of the present invention, there is provided a polyester resin prepared by the above-described process.

[0015] According to another aspect of the invention, an article is provided that includes a polyester resin. Effect of the Invention

[0016] According to the present invention, bis(glycol) terephthalates, which are platforms for various polymers, can be prepared by transesterification of BHET and glycols. In particular, this is advantageous from the viewpoint of cost, since a certain amount of BHET relative to glycol is introduced into the reaction in portions or continuously, thereby increasing the purity while using low purity BHET or reducing the amount of glycol used.

[0017] In particular, since the amount of residual ethylene glycol derivatives in the recycled bis(glycol) terephthalate according to the present invention is low, a polyester resin having a high crystallinity can be produced, and thus it is possible to produce high-value-added engineering polyester products or biodegradable polyester products with less ethylene glycol components that affect ecotoxicity from waste PET products. [Brief description of the drawings]

[0018] [Figure 1] 1 shows the change in the residual percentage of ethylene glycol derivative over time for different feeding methods during transesterification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will now be described in further detail.

[0020] In this specification, the terms referring to each component are used to distinguish them from each other and are not intended to limit the scope of the embodiments. In addition, in this specification, the singular forms "a," "an," and "the" are to be construed as including the plural unless the context indicates otherwise.

[0021] In this specification, terms such as first, second, etc. are used to describe various components. However, the components should not be limited by the terms. The terms are used only to distinguish one element from another element.

[0022] As used herein, the term "comprising" is intended to specify certain features, regions, steps, processes, elements, and / or components, without excluding the presence or addition of any other features, regions, steps, processes, elements, and / or components, unless specifically stated to the contrary.

[0023] The molecular weights of the compounds or polymers described herein, for example number average molecular weight or weight average molecular weight, are, as is well known, relative masses based on carbon 12. The units are not described but may, if necessary, be understood as molar masses (g / mole) of the same numerical value.

[0024] As used herein, a "derivative" of a particular compound refers to a compound obtained by partially converting the compound by chemical reaction or by combining it with other components, thereby containing a major portion of the compound.

[0025] As used herein, a unit or group "derived from" a particular component refers to a portion of the component that is contained in the final product of a chemical reaction such as a polymerization reaction. This may be present in a form in which the portion is modified during the reaction or combined with other components. For example, a unit or group derived from at least one monomer is contained in a chain that constitutes a polymer.

[0026] According to an aspect of the present invention, a method is provided for preparing bis(glycol) terephthalates, which are platforms for various polymers, by transesterification of bis(2-hydroxyethyl) terephthalate and glycols.

[0027] A method for preparing bis(glycol) terephthalate includes the steps of (1) feeding at least one glycol component having three or more carbon atoms to a reaction vessel, and (2) feeding bis(2-hydroxyethyl) terephthalate in portions or continuously to the reaction vessel to carry out the transesterification reaction.

[0028] Glycol Component The glycol component used in the present invention is used in a transesterification reaction with bis(2-hydroxyethyl) terephthalate to form residues in the product bis(glycol) terephthalate that constitute the polymer chains of the final polyester resin polymerized from the bis(glycol) terephthalate.

[0029] The glycol component used in the present invention may be any glycol having 3 or more carbon atoms to replace the ethylene glycol residues in the transesterification reaction.

[0030] In particular, the glycol component has a boiling point more than 10° C. higher than that of ethylene glycol, which is advantageous with respect to purification by fractional distillation during the transesterification reaction.

[0031] Specifically, the glycol component used in the transesterification reaction of the present invention may be a glycol monomer other than ethylene glycol (eg, an alkylene glycol having 3 or more carbon atoms), or a polymeric glycol (eg, a polyether).

[0032] As a more specific example, the glycol component may be at least one selected from a glycol monomer having 3 to 10 carbon atoms and a molecular weight of less than 250, and a polymeric glycol having a number average molecular weight of 400 to 5,000.

[0033] The number of carbon atoms in the glycol monomers may be, for example, 3 or more, or 4 or more, and 15 or less, 12 or less, 10 or less, or 8 or less.

[0034] As a specific example, the glycol monomer may be an alkylene diol having 3 to 10 carbon atoms. Additionally, the glycol monomer may be an aliphatic alkylene diol.

[0035] As specific examples, the glycol monomer may be selected from the group consisting of 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, and diethylene glycol.

[0036] As a more specific example, the glycol monomers include at least one selected from 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol, and may optionally further include other glycol monomers.

[0037] The glycol monomer may have a molecular weight of less than 400, less than 350, less than 300, or less than 250, for example.

[0038] The polymeric glycol may be selected from the group consisting of, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymers of ethylene oxide and tetrahydrofuran, ethylene oxide-added polypropylene glycol, polycarbonate diol, polyneopentyl glycol, poly-3-methylpentanediol, and poly-1,5-pentanediol. More specifically, the polymeric glycol may be at least one selected from the group consisting of polytetramethylene glycol, polycarbonate diol, polypropylene glycol, and ethylene oxide-added polypropylene glycol.

[0039] The polymer glycol may have a number average molecular weight of, for example, 400 or more, 500 or more, 600 or more, 700 or more, or 800 or more, or 6,000 or less, 5,000 or less, 4,000 or less, or 3,000 or less. As a specific example, the number average molecular weight of the polymer glycol may be 400 to 5,000. More specifically, it may be preferably 1,000 to 3,000 from the viewpoint of reducing phase separation.

[0040] The polymeric glycol is used in an amount of 5% to 75% by weight, specifically 10% to 60% by weight, more specifically 15% to 50% by weight, based on the weight of the final polyester resin, which is advantageous for achieving high molecular weight while improving the elasticity of the polyester resin.

[0041] Bis(2-hydroxyethyl) terephthalate In the bis(2-hydroxyethyl)terephthalate used in the present invention, the ethylene glycol residue is replaced by a glycol residue having 3 or more carbon atoms by transesterification. Bis(2-hydroxyethyl)terephthalate is an ester of two ethylene glycols and one terephthalic acid. For example, it is a compound formed as an intermediate in the process of preparing polyesters such as polyethylene terephthalate (PET) by polymerization of ethylene glycol and terephthalic acid or its ester.

[0042] The bis(2-hydroxyethyl) terephthalate used in the present invention may be obtained by depolymerization of waste polyester. For example, bis(2-hydroxyethyl) terephthalate may be obtained from waste polyester having repeat units of ethylene glycol and terephthalic acid, such as polyethylene terephthalate (PET) or glycol modified polyethylene terephthalate (PETG). Specifically, it may be obtained by well-known depolymerization methods such as glycolysis, hydrolysis, and methanolysis. In particular, bis(2-hydroxyethyl) terephthalate may be obtained by depolymerizing waste polyethylene terephthalate with ethylene glycol and then purifying it.

[0043] The recycled bis(2-hydroxyethyl) terephthalate (referred to as recycled BHET or abbreviated as r-BHET or rBHET) obtained by depolymerization of waste polyester as described above may contain by-products formed by side reactions with reagents or solvents used in various chemical steps during depolymerization of waste polyester. Thus, BHET recycled by a conventional depolymerization process contains organic and inorganic impurities in addition to BHET as the main component, and therefore its purity is not high. Since recycled BHET generally contains trace amounts of organic and inorganic impurities in addition to BHET as the main component, recycled BHET can also be viewed as a certain composition containing two or more components, i.e., BHET composition.

[0044] The impurities contained in the recycled BHET may include, for example, diethylene glycol derivatives and unreacted monomers. The total content of impurities contained in the recycled BHET may be 10 wt% or more, 15 wt% or more, or 20 wt% or more, and may be 40 wt% or less, 35 wt% or less, 30 wt% or less, or 25 wt% or less.

[0045] The purity of the recycled BHET may be measured using liquid chromatography or the like. Specifically, the purity of the recycled BHET may be calculated by measuring the percentage of the peak area of ​​BHET out of the total peak area in a spectrum obtained using high performance liquid chromatography (HPLC).

[0046] For example, the purity of the recycled BHET may be 90% or less, 85% or less, or 80% or less, or 60% or more, 65% or more, or 70% or more. Specifically, the purity of the BHET introduced into the transesterification reaction of the present invention may be 60% to 90%, more specifically, 65% to 85% or 70% to 80%.

[0047] Acid component According to the present invention, an acid component may be further introduced during the transesterification reaction. Specifically, in step (1), at least one acid component selected from dicarboxylic acids, esters and anhydrides thereof may be additionally supplied to the reaction vessel.

[0048] Specifically, the dicarboxylic acid may be at least one selected from an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid.

[0049] As an example, the dicarboxylic acid may include an aliphatic dicarboxylic acid. Specifically, the aliphatic dicarboxylic acid may be a linear, branched, or cyclic aliphatic dicarboxylic acid. The number of carbon atoms in the aliphatic dicarboxylic acid may be 4 or more, 5 or more, 6 or more, or 7 or more, and may be 20 or less, 15 or less, 13 or less, 12 or less, or 10 or less. As a specific example, the number of carbon atoms in the aliphatic dicarboxylic acid may be 4 to 20 or 4 to 12.

[0050] The aliphatic dicarboxylic acid may be, for example, but is not limited to, selected from the group consisting of adipic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, fumaric acid, glutaric acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-cyclohexanedicarboxylic acid.

[0051] As another example, the dicarboxylic acid may include an aromatic dicarboxylic acid. The number of carbon atoms in the aromatic dicarboxylic acid may be 6 or more, 7 or more, 8 or more, or 10 or more, and may be 25 or less, 20 or less, or 15 or less. As a specific example, the number of carbon atoms in the aromatic dicarboxylic acid may be 8 to 20 or 8 to 14.

[0052] The aromatic dicarboxylic acid may be selected from the group consisting of, for example, but not limited to, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 4,4'-stilbene dicarboxylic acid, 2,5-furandicarboxylic acid, and 2,5-thiophenedicarboxylic acid.

[0053] On the other hand, the additional acid component may be a dicarboxylic acid other than terephthalic acid or an ester thereof, which may constitute copolymerized units together with units derived from bis(2-hydroxyethyl) terephthalate during polycondensation after the transesterification reaction.

[0054] As a specific example, the dicarboxylic acid may include adipic acid to enhance the biodegradability of the final polyester resin. To this end, adipic acid, or its alkyl esters, specifically dimethyl adipate, may be used as the acid component in the present invention. For example, the total amount of adipic acid and its alkyl esters may be 70% to 99% by weight, based on the weight of the total acid component.

[0055] In addition, the dicarboxylic acid may further comprise an aliphatic dicarboxylic acid component, an aromatic dicarboxylic acid component, or a mixture thereof, other than adipic acid, In such an event, the total amount of dicarboxylic acids other than adipic acid may be from 1% to 30% by weight, based on the weight of the total acid component.

[0056] Transesterification The glycol and bis(2-hydroxyethyl) terephthalate undergo a transesterification reaction.

[0057] [ka]

[0058] In Reaction Scheme 1, m is an integer from 1 to 4.

[0059] The transesterification reaction may be carried out in the presence of a catalyst. Thus, when the glycol component and the acid component or bis(2-hydroxyethyl) terephthalate are fed to the reaction vessel, the catalyst may be fed together.

[0060] As a catalyst for the transesterification reaction, for example, at least one selected from the group consisting of a titanium-based catalyst, a germanium-based catalyst, an antimony-based catalyst, an aluminum-based catalyst, and a tin-based catalyst may be used.

[0061] Examples of titanium-based catalysts include tetraethyl titanate, acetyl tripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, octylene glycol titanate, triethanolamine titanate, acetylacetonate titanate, ethylacetoacetate titanate, isostearyl titanate, and titanium dioxide. Examples of germanium-based catalysts include germanium dioxide, germanium tetrachloride, germanium ethylene glycol oxide, germanium acetate, or combinations thereof. Specifically, germanium dioxide can be used as the germanium-based catalyst. Both crystalline and amorphous germanium dioxide can be used as the germanium dioxide, and glycol-soluble ones can also be used.

[0062] The amount of transesterification catalyst used may vary depending on the reaction conditions and catalyst used. As an example, a metal-based catalyst (e.g., titanium-based catalyst, tin-based catalyst) may be used such that the metal weight of the metal-based catalyst is 0.0001% to 0.005% by weight based on the total weight of glycol and bis(2-hydroxyethyl) terephthalate fed to the reaction vessel.

[0063] The transesterification reaction may be carried out in a batch or continuous mode.

[0064] As an example, the glycol component, or the glycol component together with the acid component, may be fed all at once to a reaction vessel, and bis(2-hydroxyethyl) terephthalate may be fed when the temperature reaches a certain level during the temperature increase. For example, the feeding of bis(2-hydroxyethyl) terephthalate may be performed while ethylene glycol as a by-product is removed in a nitrogen atmosphere at a temperature of 180° C. to 280° C.

[0065] According to the invention, bis(2-hydroxyethyl) terephthalate is introduced into the transesterification reaction with the glycol component in portions or continuously.

[0066] According to one embodiment, bis(2-hydroxyethyl) terephthalate is introduced into the transesterification reaction with the glycol component in two or more portions.

[0067] The number of divided introductions may be 2 or more, 3 or more, 4 or more, or 5 or more, and may be 100 or less, 50 or less, 30 or less, 20 or less, 15 or less, or 10 or less. As a specific example, the number of divided introductions may be 2 to 30 or 3 to 15.

[0068] The time interval between the divided introductions may be determined by dividing the total introduction time by the number of divided introductions. The total introduction time may be, for example, 1 hour or more, or 2 hours or more, or 5 hours or less, or 4 hours or less.

[0069] Additionally, the amount to be introduced in one of the divided introductions may be determined by dividing the total amount of bis(2-hydroxyethyl) terephthalate to be introduced into the reaction by the number of divided introductions.

[0070] According to the present invention, the components introduced into the transesterification reaction are represented by the following formula (1): 0≦G / B≦3.5...(1) Meet the following.

[0071] In formula (1), G is the total number of moles of at least one glycol component, and B is the total number of moles of bis(2-hydroxyethyl) terephthalate.

[0072] When G / B is less than 1.0, there are many ethylene glycol residues derived from BHET, which may deteriorate the physical properties of the final polyester resin. When G / B is more than 3.5, an excessive amount of glycol component is provided, which is not preferable. For example, G / B may be 1.0 or more, 1.5 or more, or 2.0 or more, and may be 3.5 or less, 3.0 or less, or 2.5 or less. As a specific example, G / B may be 1.0 to 3.0, 1.0 to 2.5, or 1.5 to 2.5.

[0073] The number of divided introductions and the total introduction amount can be more efficiently controlled by the following relation (2).

[0074]

number

[0075] In formula (2), G is the total number of moles of at least one glycol component, B is the total number of moles of bis(2-hydroxyethyl) terephthalate, and N is the number of divided introductions of bis(2-hydroxyethyl) terephthalate.

[0076] For example, the R value may be 5 or more, 6 or more, 8 or more, or 10 or more, and may be 100 or less, 50 or less, 30 or less, or 20 or less. As a specific example, it may be 4 to 50 or 6 to 30.

[0077] FIG. 1 shows the change in the residual percentage of ethylene glycol derivative over time for different feeding methods during the transesterification reaction.

[0078] Referring to FIG. 1 , (a) the amount of ethylene glycol derivatives (mainly BHET) decreases from a maximum (100%) at the beginning of the introduction as the reaction proceeds when introduced in one portion with G / B set at 2.5 (i.e., R=2.5); however, even at the time of reaction completion, the residual rate of ethylene glycol derivatives remains at a high level (30%); (b) the amount of ethylene glycol derivatives decreases more rapidly when introduced in one portion with G / B set at 4.0 (i.e., R=4.0), reaching a low level (10%) at the time of reaction completion; and (c) the amount of ethylene glycol derivatives is maintained below a certain level (40%) throughout the reaction process when introduced in four portions with G / B set at 2.5 (i.e., R=10.0), and in particular reaches a very low level (3%) at the time of reaction completion.

[0079] In the conventional processes (a) and (b) of Figure 1, an excess amount of glycol component is required to reduce the residual percentage of the final ethylene glycol derivative, which increases the cost, whereas in the process (c) of the present invention, the residual amount of ethylene glycol derivative in the final product can be at a very low level without even increasing the amount of glycol component.

[0080] According to another embodiment, bis(2-hydroxyethyl) terephthalate is introduced continuously into the transesterification reaction with the glycol component.

[0081] The total time for continuous introduction may be, for example, 1 hour or more, or 2 hours or more, and may be 5 hours or less, or 4 hours or less.

[0082] For example, the continuous introduction may be the introduction of a constant amount of bis(2-hydroxyethyl) terephthalate per hour. The amount of introduction per hour may be determined by dividing the total amount of bis(2-hydroxyethyl) terephthalate to be introduced into the reaction by the total introduction time.

[0083] As a specific example, bis(2-hydroxyethyl) terephthalate may be dissolved in water at about 80-100° C. to prepare an aqueous BHET solution having a concentration of about 10-20% by weight, and the solution may be continuously introduced. The continuous introduction may be carried out from the start of the transesterification reaction until one hour before the completion of the reaction. For the continuous introduction of a constant amount per hour, a dropping funnel may be used at the laboratory level, or a metering feeder may be used at the commercial level.

[0084] When the introduction of bis(2-hydroxyethyl) terephthalate in portions or continuously is completed, the reaction conditions may be maintained until the transesterification reaction is completed. In addition, the process of removing ethylene glycol as a by-product may be continued during the transesterification reaction. The removal of ethylene glycol may be carried out by a distillation process using the difference in boiling point with other components. The ethylene glycol thus distilled off may be recovered by cooling and reused in other processes.

[0085] The end point of the transesterification reaction may be determined by considering the theoretical amount of ethylene glycol formed from bis(2-hydroxyethyl) terephthalate by the transesterification reaction, or as the point at which no more by-products are released.

[0086] The pressure during the ester exchange reaction is, for example, 0.01 kg / cm 2 More than 0.05kg / cm 2 or more than 0.1kg / cm 2 It may be 0.5kg / cm or more. 2 Below, 0.3kg / cm 2 Below 0.2kg / cm 2 or less than 1.5kg / cm 2The temperature during the ester exchange reaction may be 140° C. or more, 160° C. or more, 180° C. or more, or 200° C. or more, and may be 300° C. or less, 280° C. or less, 270° C. or less, 250° C. or less, or 220° C. or less. In addition, the ester exchange reaction may be carried out under a nitrogen atmosphere. As a specific example, the ester exchange reaction may be carried out under a nitrogen atmosphere at a pressure of 0.05 kgf / cm. 2 ~0.2kgf / cm 2 and at a temperature of 180°C to 280°C.

[0087] The pressure and temperature conditions during the transesterification reaction may be adjusted appropriately according to the specific characteristics of the polyester to be produced, the ratio of each component, or the process conditions. For example, the transesterification reaction may be carried out at a temperature of 180°C or higher to facilitate the removal of ethylene glycol, a by-product formed during the transesterification reaction. In addition, it may be carried out at a temperature 10°C lower than the boiling point of the glycol component to reduce the loss of the glycol component for substitution. As a specific example, when 1,4-butanediol is used as the glycol component, the temperature may be adjusted to 180°C to 220°C. Alternatively, when 1,4-cyclohexanedimethanol is used, the temperature may be adjusted to 200°C to 270°C.

[0088] The products of the transesterification reaction primarily include bis(glycol) terephthalate and its derivatives, in which the ethylene glycol residues in bis(2-hydroxyethyl) terephthalate are replaced with other glycol residues.

[0089] According to one embodiment, the recycled bis(glycol) terephthalate obtained by transesterification comprises a compound represented by the following formula 1:

[0090] [ka]

[0091] In formula 1, -OR-OH is a group derived from a glycol moiety having 3 or more carbon atoms, and m is an integer of 1 to 4.

[0092] For example, in formula 1, R is a group derived from a glycol component having 3 or more carbon atoms, and the group may be an alkylene group having 3 to 10 carbon atoms, or a group in which two or more identical or different alkylene groups having 3 to 10 carbon atoms are bonded via an ether group or a carbonate group.

[0093] In addition, the recycled bis(glycol) terephthalate may contain two or more compounds represented by Formula 1 or derivatives thereof.

[0094] On the other hand, the product of the above-mentioned transesterification reaction may contain unreacted materials or by-products in addition to the bis(glycol) terephthalate.

[0095] As an example, the transesterification product may include components derived from recycled bis(2-hydroxyethyl) terephthalate used as a starting material. Specifically, the transesterification product may include ethylene glycol and its derivatives.

[0096] The ethylene glycol derivative may be ethylene glycol or a compound having a residue thereof, for example, an ester of ethylene glycol. Specifically, the ethylene glycol derivative may include bis(2-hydroxyethyl) terephthalate, 2-hydroxyethyl terephthalate, 2-hydroxyethyl-4-hydroxybutyl terephthalate, bis(diethylene glycol) terephthalate, 2-hydroxydiethyl-diethylene glycol terephthalate, 4-hydroxybutyl-diethylene glycol terephthalate, ethylene glycol, and oligomers thereof. It may be mainly bis(2-hydroxyethyl) terephthalate.

[0097] The total content of ethylene glycol and its derivatives present in the product of the above transesterification reaction may be 20% by weight or less. Thus, the total content of ethylene glycol and its derivatives in the recycled bis(glycol) terephthalate may be 20% by weight or less. For example, the total content of ethylene glycol and its derivatives in the recycled bis(glycol) terephthalate may be 15% by weight or less, 10% by weight or less, or 5% by weight or less.

[0098] Thus, the recycled bis(glycol) terephthalates of the present invention can be used to produce polyester resins having high crystallinity.

[0099] Preparation of polyester resin (polycondensation reaction) The product of the transesterification reaction (ie, the mixture containing recycled bis(glycol) terephthalate) may be subjected to a polycondensation reaction to prepare a polyester resin.

[0100] In other words, a method for preparing a polyester resin according to one embodiment of the present invention includes the steps of (1) supplying at least one glycol component having 3 or more carbon atoms to a reaction vessel, (2) supplying bis(2-hydroxyethyl) terephthalate to the reaction vessel in portions or continuously to carry out an ester exchange reaction, and (3) subjecting the product of the ester exchange reaction to a polycondensation reaction, wherein the components supplied to the reaction vessel satisfy the above-mentioned relationship (1).

[0101] Referring to Reaction Scheme 2 below, the product of the transesterification reaction includes a bis(glycol) terephthalate monomer or oligomer (such as a dimer or trimer). It may further include excess glycol components that remain without participating in the transesterification reaction. The bis(glycol) terephthalate monomer or oligomer is subjected to a polycondensation reaction in the presence of a catalyst to prepare a polyester resin, during which glycol is formed as a by-product of the polycondensation reaction.

[0102] [ka]

[0103] In Reaction Scheme 2, m is an integer from 1 to 4, and n represents the number of repeat units in the polymer chain.

[0104] The polycondensation reaction may be carried out, for example, by reacting the transesterification reaction product at a temperature of 150° C. to 300° C. under reduced pressure conditions of 0.01 mmHg to 600 mmHg for 1 hour to 24 hours.

[0105] The temperature in the polycondensation reaction may be 150°C to 300°C, specifically 200°C to 290°C, more specifically 260°C to 280°C. In addition, the pressure in the polycondensation reaction may be 0.01mmHg to 600mmHg, specifically 0.05mmHg to 200mmHg, more specifically 0.1mmHg to 100mmHg. Since reduced pressure conditions are adopted in the polycondensation reaction, glycol, which is a by-product of the polycondensation reaction, can be removed from the system. When the pressure in the polycondensation reaction exceeds the range of 0.01mmHg to 400mmHg, the removal of the by-product may be insufficient. In addition, when the temperature in the polycondensation reaction is lower than 150°C, glycol, which is a by-product of the reaction, cannot be efficiently removed from the system, and therefore the intrinsic viscosity of the final reaction product is low, and the physical properties of the final polyester resin are deteriorated. If the temperature in the polycondensation reaction exceeds 300° C., the possibility of yellowing of the final polyester resin increases. In addition, the polycondensation reaction may be carried out for a required time, for example, an average residence time of 1 hour to 24 hours, until the intrinsic viscosity of the final reaction product reaches an appropriate level.

[0106] As a catalyst for the polycondensation reaction, for example, at least one selected from the group consisting of a titanium-based catalyst, a germanium-based catalyst, an antimony-based catalyst, an aluminum-based catalyst, and a tin-based catalyst may be used.

[0107] Examples of titanium-based catalysts include tetraethyl titanate, acetyl tripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, octylene glycol titanate, triethanolamine titanate, acetylacetonate titanate, ethylacetoacetate titanate, isostearyl titanate, titanium dioxide, etc. Examples of germanium-based catalysts include germanium dioxide, germanium tetrachloride, germanium ethylene glycol oxide, germanium acetate, or combinations thereof. Specifically, germanium dioxide can be used as the germanium-based catalyst. Both crystalline and amorphous germanium dioxide can be used as the germanium dioxide, and glycol-soluble ones can also be used.

[0108] In addition, one or more glycol components and one or more acid components may be further introduced into the polycondensation reaction.

[0109] The specific type of the glycol component(s) additionally introduced may be the same as the one or more glycol components fed to the reaction vessel in step (1) above.

[0110] For example, the glycol component may be a glycol monomer (e.g., an alkylene glycol) or a polymeric glycol (e.g., a polyether). Specifically, the glycol component may be 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,7-hexanediol, 1,8-hexanediol, 1,9-hexanediol, 2,10-hexanediol, 2,11-hexanediol, 2,12-hexanediol, 2,13-hexanediol, 2,14-hexanediol, 2,15-hexanediol, 2,16-hexanediol, 2,17-hexanediol, 2,18-hexanediol, 2,19-hexanediol, 2,20-hexanediol, 2,21-hexanediol, 2,22-hexanediol, 2,23-hexanediol, 2,24-hexanediol, 2,25-hexanediol, 2,26-hexanediol, 2,27-hexanediol, 2,28-hexanediol, 2,29-hexanediol, 2,30-hexanediol, 2,31-hexanediol, 2,32-hexanediol, 2,33-hexanediol, 2,34-hexanediol, 2,35-hexanediol, 2,36-hexanediol, 2,37-hexanediol, 2,38-hexanedi ,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymers of ethylene oxide and tetrahydrofuran, ethylene oxide-added polypropylene glycol, polycarbonate diol, polyneopentyl glycol, poly-3-methylpentanediol, and poly-1,5-pentanediol.

[0111] In addition, an acid component may be additionally introduced in step (1) or (3). For example, the acid component may be at least one selected from dicarboxylic acids and their esters. Specifically, the acid component may be selected from the group consisting of adipic acid, sebacic acid, succinic acid, isodecyl succinic acid, maleic acid, fumaric acid, glutaric acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 4,4'-stilbene dicarboxylic acid, 2,5-furandicarboxylic acid, and 2,5-thiophenedicarboxylic acid.

[0112] Alternatively, ethylene glycol may be introduced as an additional glycol component and terephthalic acid may be introduced as an additional acid component in the polycondensation reaction, if desired.

[0113] Polyester Resin According to another aspect of the present invention, there is provided a polyester resin prepared by the above-described process.

[0114] In other words, the polyester resin is prepared by polycondensation of recycled bis(glycol) terephthalate obtained by transesterification, and thus contains units derived from components derived from recycled bis(glycol) terephthalate.

[0115] Additionally, because the recycled bis(glycol) terephthalate contains unreacted glycol and acid components, or by-products such as ethylene glycol, in addition to the bis(glycol) terephthalate, units derived from these components may be incorporated into the polyester resin by subsequent polycondensation.

[0116] Specifically, the polyester resin may include units derived from one or more glycol components and units derived from one or more acid components. The one or more glycol components may be the glycol monomers or polymeric glycols exemplified above. The one or more acid components may be the aliphatic dicarboxylic acids and aromatic dicarboxylic acids exemplified above.

[0117] The glycol component and acid component constituting the polyester resin are derived from the bis(2-hydroxyethyl) terephthalate and glycol component initially introduced for the preparation of the polyester resin, or from recycled bis(glycol) terephthalate prepared therefrom, and an acid component additionally introduced.

[0118] The polyester resin may be a homopolymer or copolymer resin. As a specific example, the polyester resin may be at least one selected from polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polybutylene adipate-co-terephthalate (PBAT), polypropylene adipate-co-terephthalate (PPAT), polycyclohexane dimethyl terephthalate (PCT), and thermoplastic polyester elastomer (TPEE).

[0119] The polyester resin may have a total content of ethylene glycol and diethylene glycol residues below a certain level. For example, the total content of ethylene glycol and diethylene glycol residues of the polyester resin may be 15 mol% or less, 10 mol% or less, 8 mol% or less, 7.5 mol% or less, 7 mol% or less, 6 mol% or less, 5 mol% or less, 4 mol% or less, or 3 mol% or less, based on the moles of total glycol residues. In addition, the total content of ethylene glycol and diethylene glycol residues may be 0 mol% or more, 0.01 mol% or more, 0.02 mol% or more, or 0.03 mol% or more. The total content of ethylene glycol and diethylene glycol residues may be: 1 The H-NMR spectrum of the resulting polyester resin may be analyzed to determine the amount of the residues. These residues may be derived from ethylene glycol, diethylene glycol, and their derivatives. As a specific example, the polyester resin may be 1 When measured by H-NMR, the total content of ethylene glycol residues and diethylene glycol residues may be 0.01 mol % to 10 mol % based on the mole number of the total glycol residues. If the content is within the above range, the crystallization degree of the polyester resin can be increased, and therefore the heat resistance and mechanical properties can be improved.

[0120] The polyester resin may have an intrinsic viscosity at 35° C. of 0.5 dl / g to 1.5 dl / g. For example, the intrinsic viscosity at 35° C. of the polyester resin may be 0.5 dl / g or more, 0.55 dl / g or more, 0.6 dl / g or more, 0.7 dl / g or more, 0.8 dl / g or more, 0.9 dl / g or more, or 1.0 dl / g or more, and may be 1.5 dl / g or less, 1.4 dl / g or less, 1.3 dl / g or less, 1.2 dl / g or less, 1.1 dl / g or less, 1.0 dl / g or less, or 0.7 dl / g or less. As a specific example, the polyester resin may have an intrinsic viscosity at 35° C. of 0.55 to 1.1 dl / g or 0.6 to 0.7 dl / g.

[0121] The polyester resin prepared by the above process may have a state such as chip, pellet, or powder before molding. It may also have the shape of a molded article formed by a separate molding process such as extrusion or injection, for example, in film or sheet form, or various injected part forms for automotive, electrical, and industrial purposes.

[0122] Thus, the present invention also provides an article comprising a polyester resin.

[0123] In particular, the polyester resin of the present invention can be used as a high-value-added engineering polyester product or a biodegradable polyester product with a low content of ethylene glycol components that affect ecotoxicity.

[0124] Aspects of the invention In the following, preferred embodiments are presented for understanding the present invention. However, the following examples are provided only to help the present invention to be easily understood, and are not intended to limit the scope of the present invention. EXAMPLES

[0125] Preparation Example 1: Preparation of bis(2-hydroxyethyl) terephthalate A stainless steel (SUS) reactor was charged with 1,000 g of waste polyester resin, 4,000 g of ethylene glycol, and 3.5 g of zinc acetate anhydride. The temperature inside the reactor was raised to 196°C, and depolymerization by glycolysis reaction was carried out for 4 hours. The reaction result was cooled to 30°C, and crystallization of bis(2-hydroxyethyl) terephthalate was carried out for 2 hours. The resulting slurry of bis(2-hydroxyethyl) terephthalate and ethylene glycol was subjected to solid-liquid separation in a centrifuge. The bis(2-hydroxyethyl) terephthalate obtained by centrifugation was washed twice with sufficient distilled water, and the residual solvent was removed in an oven to obtain about 1,100 g of a final product containing bis(2-hydroxyethyl) terephthalate.

[0126] Example 1 Step (1): Preparation of bis(glycol) terephthalate by transesterification A 1-liter reaction vessel for transesterification, equipped with a column and a condenser and capable of being cooled by water, was charged with 108.0 g of 1,4-butanediol (BD) as a glycol component and 94 mg of tetrabutyl titanate (TBT) as a reaction catalyst. The pressure in the reaction vessel was then reduced to 0.1 kg / cm by flowing nitrogen. 2 The temperature was adjusted to 50° C., and the temperature was increased while stirring and maintaining the pressure. When the temperature in the reaction vessel reached about 200° C. while increasing the temperature to 220° C. over 3 hours, 127.0 g of bis(2-hydroxyethyl) terephthalate (BHET) obtained in Preparation Example 1 was divided into five portions and fed to carry out the transesterification reaction. During the reaction, glycol as a by-product was discharged through a column and a condenser. Even after the addition of BHET was completed, the transesterification reaction was continued while maintaining 220° C. until the discharge of glycol stopped. As soon as the transesterification reaction was completed, the nitrogen in the pressurized reaction vessel was released to the outside to reduce the pressure in the reaction vessel to normal pressure, and then the resultant product in the reaction vessel (mixture containing bis(2-hydroxyethyl) terephthalate) was transferred to a 0.5 liter reaction vessel capable of reaction under reduced pressure.

[0127] Step (2): Preparation of polyester resin by polycondensation reaction The pressure in the reaction vessel was reduced from normal pressure to 5.0 torr (absolute pressure: 5 mmHg) over 30 minutes. At the same time, the temperature of the reaction vessel was increased to 245° C. over 1 hour, and the polycondensation reaction was carried out while maintaining the pressure in the reaction vessel at 1 torr (absolute pressure: 1 mmHg) or less. At the start of the polycondensation reaction, the stirring speed could be set high. As the polycondensation reaction proceeded, the by-product glycol component was discharged from the reaction vessel. When the stirring power weakened due to an increase in the viscosity of the reactants, or when the temperature of the reactants rose above the set temperature, the stirring speed was adjusted accordingly. The polycondensation reaction was carried out until the intrinsic viscosity (IV) of the mixture (melt) in the reaction vessel reached 0.75-0.85 dl / g. When the intrinsic viscosity of the mixture in the reaction vessel reached the desired level, the mixture was then discharged outside the reaction vessel to form strands. The strands were solidified using a cooling liquid and then granulated to an average weight of about 12-14 mg, yielding 109.7 g of polyester resin.

[0128] Example 2 A polyester resin was obtained by the same procedure as in Example 1, except that in step (1), 111.7 g of 1,4-cyclohexanedimethanol (CHDM) was used as the glycol component, 127.0 g of BHET was divided into six portions and fed, and the final temperature during the ester exchange reaction was set to 260°C, and in step (2), the final temperature during the polycondensation reaction was adjusted to 295°C.

[0129] Example 3 A polyester resin was obtained by the same procedure as in Example 1, except that in step (1), 127.0 g of BHET was divided into eight portions and fed.

[0130] Example 4 A polyester resin was obtained by the same procedure as in Example 1, except that in step (1), 127.0 g of BHET was fed in 12 portions.

[0131] Example 5 A polyester resin was obtained by the same procedure as in Example 1, except that in step (1), 127.0 g of BHET was dissolved in 850 g of purified water at 90° C. to prepare a 13 wt % aqueous BHET solution, and then a dropping funnel was used to continuously feed the aqueous BHET solution at a constant rate of 4.07 g / min for 4 hours.

[0132] Example 6 A polyester resin was obtained by the same procedure as in Example 1, except that in step (1), 93.1 g of 1,3-propanediol (PDO) was used as the glycol component, 127.0 g of BHET was divided into four portions and fed, and the final temperature during the ester exchange reaction was set to 200°C, and in step (2), the final temperature during the polycondensation reaction was adjusted to 245°C.

[0133] Example 7 A polyester resin was obtained by the same procedure as in Example 1, except that in step (1), 95.6 g of 1,4-butanediol (BD) and 87.9 g of polytetramethylene glycol (PTMG, Mn 1,000) were used as glycol components, the final temperature during the ester exchange reaction was set to 220°C, and in step (2), the final temperature during the polycondensation reaction was adjusted to 245°C.

[0134] Example 8 A polyester resin was obtained by the same procedure as in Example 7, except that in step (1), 95.6 g of 1,4-butanediol (BD) and 87.9 g of poly-1,3-propylene glycol (PO3G, Mn 1,000) were used as the glycol component.

[0135] Example 9 A polyester resin was obtained by the same procedure as in Example 7, except that in step (1), 95.6 g of 1,4-butanediol (BD) and 111.3 g of ethylene oxide-added polypropylene glycol (EO-PPG, Mn 2,400) were used as the glycol components.

[0136] Example 10 In step (1), a polyester resin was obtained by the same procedure as in Example 1, except that 72.0 g of 1,4-butanediol (BD) was used as the glycol component, 63.5 g of BHET was divided into four portions and fed, and 36.5 g of adipic acid (AA) was used as the additional acid component.

[0137] Example 11 A polyester resin was obtained by the same procedure as in Example 10, except that in step (1), 60.8 g of 1,3-propanediol (PDO) was used as the glycol component.

[0138] Comparative Example 1 A polyester resin was obtained by the same procedure as in Example 1, except that in step (1), BHET was fed in one portion together with 1,4-butanediol (BD) at the beginning.

[0139] Comparative Example 2 A polyester resin was obtained by the same procedure as in Comparative Example 1, except that in step (1), the amount of 1,4-butanediol (BD) used was increased to 180.1 g.

[0140] Comparative Example 3 A polyester resin was obtained by the same procedure as in Example 2, except that in step (1), BHET was fed in one portion together with 1,4-cyclohexanedimethanol (CHDM) at the beginning.

[0141] Comparative Example 4 A polyester resin was obtained by the same procedure as in Example 7, except that in step (1), BHET was fed in one batch together with polytetramethylene glycol (PTMG, Mn 1,000) at the beginning.

[0142] Comparative Example 5 A polyester resin was obtained by the same procedure as in Example 6, except that in step (1), BHET was fed in one portion together with 1,3-propanediol (PDO) at the beginning.

[0143] Comparative Example 6 A polyester resin was obtained by the same procedure as in Example 10, except that in step (1), BHET was fed in one portion together with 1,4-butanediol (BD) and adipic acid (AA) at the beginning.

[0144] Comparative Example 7 A polyester resin was obtained by the same procedure as in Example 10, except that in step (1), BHET was fed in one batch together with 1,3-propanediol (PDO) and adipic acid (AA) at the beginning.

[0145] The components used in the above-mentioned Examples and Comparative Examples, and the amounts used thereof, are shown in Tables 1 and 2 below.

[0146] In addition, the glycol / rBHET ratio (G / B) of the following relational formula (1) and the rBHET introduction ratio (R) of the following relational formula (2) were calculated and are shown in Table 1 below. 1.0≦G / B≦3.5...(1)

[0147] In formula (1), G is the total number of moles of at least one glycol component, and B is the total number of moles of bis(2-hydroxyethyl) terephthalate.

[0148]

number

[0149] In formula (2), G is the total number of moles of at least one glycol component, B is the total number of moles of bis(2-hydroxyethyl) terephthalate, and N is the number of divided introductions of bis(2-hydroxyethyl) terephthalate.

[0150] Test Example 1: Purity of r-BHET The purity of r-BHET obtained in Preparation Example 1 was measured by diluting 0.01 g of the sample in 20 ml of methanol or chloroform using liquid chromatography. The component contents (area %) in the total r-BHET were analyzed by summing the peak areas in the measured spectrum, and 75-80% BHET and 20-25% other oligomers, DEG derivatives, and unreacted monomers were confirmed.

[0151] Test Example 2: Content of EG and DEG residues Each polyester resin was dissolved in CDCl3 solvent at a concentration of 3 mg / ml, and its structure was measured at 25°C using a nuclear magnetic resonance device (JEOL, 600 MHz FT-NMR). 1 H-NMR spectra were obtained and the total content (mol%) of ethylene glycol and diethylene glycol residues was calculated based on the total moles of residues derived from all glycols (EG, DEG, BD, PDO, PTMG, PO3G, and EO-PPG, etc.) by analyzing the above spectra.

[0152] Test Example 3: Intrinsic Viscosity The polyester resin was dissolved in orthochlorophenol (OCP) at 150° C. at a concentration of 0.12% to obtain a solution, and the intrinsic viscosity was measured using an Ubbelohde viscometer in a thermostatic bath at 35° C. Specifically, the temperature of the viscosity tube was maintained at 35° C., and the time required for the solvent to pass between specific inner sections of the viscosity tube (flow time) and the time required for the solution to pass and obtain the specific viscosity were used to calculate the intrinsic viscosity.

[0153] Test Example 4: Tm and ΔH f Each polyester resin was dried under vacuum at 50° C. for 15 hours, melted, quenched, and then heated at 10° C. / min in a differential scanning calorimeter (DSC, TA Instruments) for testing. The highest point of the endothermic peak due to resin melting was used as the melting point (Tm), and the heat of fusion (ΔH f) was calculated as the area of ​​the endothermic peak.

[0154] The test results are shown in Tables 1 and 2 below.

[0155] [Table 1]

[0156] [Table 2]

[0157] As can be seen from Tables 1 and 2, in Examples 1 to 11 according to the present invention in which the transesterification reaction was carried out while feeding rBHET in portions or continuously under conditions in which the rBHET introduction ratio (R) was 5 or more, the total content of EG and DEG residues was as low as 10 mol% or less. In contrast, in Comparative Examples 1 to 7 in which the transesterification reaction was carried out while feeding rBHET in a single portion, the total content of EG and DEG residues exceeded 10 mol%.

[0158] As a result, the polyester resins of the examples have higher melting points (T) than those of the comparative polyester resins prepared with the same glycol / rBHET ratio (G / B). m ) and heat of fusion (ΔH f ) indicating excellent crystallinity.

Claims

1. (1) providing at least one glycol component having 3 or more carbon atoms to a reaction vessel; (2) supplying bis(2-hydroxyethyl) terephthalate in portions or continuously to a reaction vessel and carrying out an ester exchange reaction; Including, The following relation (1): 0≦G / B≦3.5 ．．．（１） is fulfilled, A method for preparing bis(glycol) terephthalate, wherein in formula (1), G is the total number of moles of at least one glycol component and B is the total number of moles of bis(2-hydroxyethyl) terephthalate.

2. 2. The method for preparing a bis(glycol) terephthalate according to claim 1, wherein the glycol component in step (1) is at least one selected from glycol monomers having 3 to 10 carbon atoms and having a molecular weight of less than 250, and polymeric glycols having a number average molecular weight of 400 to 5,000.

3. 2. The method for preparing bis(glycol) terephthalate according to claim 1, wherein in step (1), at least one acid component selected from dicarboxylic acids and esters and anhydrides thereof is additionally fed to the reaction vessel.

4. 4. The method for preparing a bis(glycol) terephthalate of claim 3, wherein the dicarboxylic acid comprises an aliphatic dicarboxylic acid.

5. 2. The process for preparing bis(glycol) terephthalate according to claim 1, wherein the purity of the bis(2-hydroxyethyl) terephthalate provided in step (2) is 60% to 90%.

6. The method for preparing bis(glycol) terephthalate according to claim 1, wherein the bis(2-hydroxyethyl) terephthalate is obtained by depolymerization of waste polyester.

7. In step (2), bis(2-hydroxyethyl) terephthalate is introduced into the transesterification reaction in two or more portions, and the reaction is carried out according to the following formula (2): [0010] The introduction ratio (R) of bis(2-hydroxyethyl) terephthalate is 5 or more; In formula (2), G is the total number of moles of at least one glycol component, B is the total number of moles of bis(2-hydroxyethyl)terephthalate, and N is the number of divided introductions of bis(2-hydroxyethyl)terephthalate.

2. A process for preparing the bis(glycol) terephthalate of claim 1.

8. 2. The method for preparing bis(glycol) terephthalate according to claim 1, wherein the introduction of bis(2-hydroxyethyl) terephthalate is carried out while ethylene glycol as a by-product is removed in a nitrogen atmosphere at a temperature of 180° C. to 280° C.

9. (1) providing at least one glycol component having 3 or more carbon atoms to a reaction vessel; (2) supplying bis(2-hydroxyethyl) terephthalate in portions or continuously to a reaction vessel and carrying out an ester exchange reaction; (3) subjecting the product of the transesterification reaction to a polycondensation reaction; Including, The following relation (1): 0≦G / B≦3.5 ．．．（１） is fulfilled, In the formula (1), G is the total number of moles of at least one glycol component, and B is the total number of moles of bis(2-hydroxyethyl) terephthalate. A method for preparing a polyester resin.

10. The at least one glycol component in step (1) is 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclo ...

10. The method for preparing the polyester resin of claim 9, wherein the copolymer is selected from the group consisting of xanediol, 1,4-cyclohexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymers of ethylene oxide and tetrahydrofuran, ethylene oxide-added polypropylene glycol, polycarbonate diol, polyneopentyl glycol, poly-3-methylpentanediol, and poly-1,5-pentanediol.

11. An acid component is additionally introduced in step (1) or (3); the acid component is selected from the group consisting of adipic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, fumaric acid, glutaric acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 4,4'-stilbene dicarboxylic acid, 2,5-furandicarboxylic acid, and 2,5-thiophenedicarboxylic acid; A process for preparing the polyester resin of claim 9.

12. A polyester resin prepared by the method of any one of claims 9 to 11.

13. １ 13. The polyester resin of claim 12, having a total content of ethylene glycol and diethylene glycol residues of 0.01 mol % to 10 mol %, based on moles of total glycol residues, as measured by H-NMR.

14. The polyester resin of claim 12 having an intrinsic viscosity at 35° C. of 0.5 dl / g to 1.5 dl / g.

15. 13. An article comprising the polyester resin of claim 12.

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