Process for purifying bis-2-hydroxyethyl terephthalate and polyester resins comprising the same

Abstract

The present disclosure relates to a process for purifying bis-2-hydroxyethyl terephthalate in high purity and a polyester resin comprising the bis-2-hydroxyethyl terephthalate.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method for purifying bis-2-hydroxyethyl terephthalate in high purity and a polyester resin comprising the same. TECHNICAL BACKGROUND

[0002] Polyethylene terephthalate (PET) can be recycled after use, and a recycling method is mainly divided into physical recycling and chemical recycling. The physical recycling is washing PET and then crushing it into large particles or flakes for use, while the chemical recycling is to recover monomers of PET through a chemical reaction. In the chemical recycling, PET is decomposed into monomers through a chemical reaction, and the produced monomers can be reused as raw materials for polyester production. The monomers produced by decomposition have the same chemical properties as the monomers used in the initial polymer synthesis.

[0003] PET can be prepared by condensation of terephthalic acid (TPA) with ethylene glycol (EG) or by reaction of dimethyl terephthalate (DMT) with EG. Both methods are about polymerization of the monomer of PET, bis(2-hydroxyethyl) terephthalate (BHET), into PET. In the recycling of PET, the monomer BHET can be obtained by depolymerizing PET with EG. The BHET obtained from depolymerization can be reused for PET polymerization after being separated from the by-products of depolymerization and purified.

[0004] U.S. Patent No. 9127136 attempts to separate and purify BHET by using liquid chromatography of a mixed solvent of methanol and water. However, when a mixed solvent is used in a separation and purification process, there can be difficulties in a recovery process of the mixed solvent. In addition, U.S. Patent Nos. 3120560 and 3268575 use water, ethylene dichloride, hexanol, and the like as a crystallization solvent for BHET purification. However, when ethylene dichloride is used as a solvent, crystallization occurs at a high temperature of 70°C or higher, and requires separation at a high temperature. In addition, U.S. Patent No. 3632830 attempts to purify by BHET crystallization using aromatic solvents such as benzene, toluene, and xylene. European Patent Publication No. EP 0723951 attempts to purify BHET by crystallizing BHET obtained by filtration after depolymerization of PET.

[0005] Japanese Patent Publication No. 2000-169623 discloses a BHET crystallization and purification process using ethylene glycol, but it is difficult to completely remove by-products, and low-quality polyester having a color change is produced from recycled polyester produced using the BHET. In addition, Japanese Patent Publication Nos. 2008-088096, 2000-053802, 2016-536291, etc. disclose purification of BHET obtained by depolymerizing PET, but there is a problem in that the purified BHET and polyester produced using the BHET have unsatisfactory color quality.

[0006] Accordingly, the present inventors have conducted extensive research into a method for purifying bis-2-hydroxyethyl terephthalate that can significantly improve the quality of bis-2-hydroxyethyl terephthalate recovered from chemical recycling of polyester. As a result, it was confirmed that when activated carbon is used in an aqueous solution of bis-2-hydroxyethyl terephthalate, bis-2-hydroxyethyl terephthalate can be purified at a high purity, and the color of polyester prepared using the bis-2-hydroxyethyl terephthalate can also be improved, thereby completing the present invention. DETAILED DESCRIPTION

[0008] TECHNICAL PROBLEM

[0009] In the present disclosure, a method for purifying bis-2-hydroxyethyl terephthalate at a high purity and a polyester resin comprising the same are provided.

[0010] TECHNICAL SOLUTION

[0011] To solve the above problems, a method for purifying bis-2-hydroxyethyl terephthalate is provided, the method comprising the steps of:

[0012] 1) mixing bis-2-hydroxyethyl terephthalate and water;

[0013] 2) adding activated carbon to the mixture of step 1; and

[0014] 3) recovering bis-2-hydroxyethyl terephthalate from the mixture of step 2.

[0015] Hereinafter, the present invention will be described in detail with respect to each step.

[0016] (Step 1)

[0017] Step 1 of the present disclosure is a step of mixing bis-2-hydroxyethyl terephthalate and water to prepare an aqueous solution of bis-2-hydroxyethyl terephthalate.

[0018] Bis-2-hydroxyethyl terephthalate to be purified in the present disclosure is not particularly limited, but bis-2-hydroxyethyl terephthalate obtained by depolymerization of a polyester or a post-consumer recycled polyester is used.

[0019] Generally, in the preparation of bis-2-hydroxyethyl terephthalate using post-consumer collected recycled PET, the PET is placed into EG and depolymerized by boiling at a high temperature, but impurities such as dimers are produced together with the bis-2-hydroxyethyl terephthalate. Further, when the EG is boiled at a high temperature under oxygen-uncontrolled conditions, it becomes yellow and a discoloration chemical can occur. Further, if the post-consumer collected recycled PET is colored, there can be an excess of pigments or dyes. During the depolymerization, these dyes and pigments are dissolved in the EG as they are, and if they are not properly purified, they can be mixed with the formed bis-2-hydroxyethyl terephthalate.

[0020] Therefore, in order to remove substances other than bis-2-hydroxyethyl terephthalate in the purification process as described above, the present disclosure is characterized in that an aqueous solution of bis-2-hydroxyethyl terephthalate is prepared, and then activated carbon is used, as will be described later.

[0021] Preferably, bis-2-hydroxyethyl terephthalate and water are mixed in a weight ratio of 20:80 to 90:10 in step 1.

[0022] Preferably, the temperature of the water in step 1 is preferably 50°C to 90°C. This means the temperature of the aqueous solution of bis-2-hydroxyethyl terephthalate prepared in step 1, and the solubility of bis-2-hydroxyethyl terephthalate can increase in the temperature range above. More preferably, the temperature of the water is 60°C to 90°C.

[0023] (Step 2)

[0024] Step 2 of the present disclosure is a purification step of adding activated carbon to the aqueous solution of bis-2-hydroxyethyl terephthalate prepared in step 1. With this step, impurities in the aqueous solution of bis-2-hydroxyethyl terephthalate are adsorbed to the activated carbon, thereby removing the impurities.

[0025] Preferably, the activated carbon is added in an amount of 0.1 wt% to 5.0 wt% based on the weight of the mixture of step 1.

[0026] Meanwhile, after the activated carbon is added, the aqueous solution of bis-2-hydroxyethyl terephthalate can be stirred in order to efficiently remove the impurities. Further, the stirring time and stirring speed can be controlled by checking the degree of removal of the impurities under the naked eye.

[0027] (Step 3)

[0028] Step 3 of the present disclosure is a step of recovering bis-2-hydroxyethyl terephthalate from the mixture of Step 2.

[0029] The recovery is not particularly limited, as long as the bis-2-hydroxyethyl terephthalate produced is separated from the activated carbon, and can be preferably performed by filtration. Thus, Step 3 can be performed by filtering the mixture of Step 2 to recover a filtrate. Since the recovered filtrate contains purified bis-2-hydroxyethyl terephthalate, the recovered filtrate can be used for the production of a polyester copolymer to be described later, without a separate additional process.

[0030] Further, in order to further purify the bis-2-hydroxyethyl terephthalate, bis-2-hydroxyethyl terephthalate crystals can be induced from the recovered filtrate, and the resulting crystals can be recovered.

[0031] Specifically, the filtrate can be cooled to 10°C to 40°C to recover bis-2-hydroxyethyl terephthalate crystals. The resulting crystals can be recovered by separating the resulting bis-2-hydroxyethyl terephthalate crystals and the solution, preferably by centrifugal separation.

[0032] (Production of a polyester copolymer)

[0033] Since the bis-2-hydroxyethyl terephthalate purified by the purification method described above has a high purity by removing impurities, it can be used for the production of a polyester copolymer.

[0034] Specifically, there is provided a method for producing a polyester copolymer, the method comprising the following steps:

[0035] 1) producing an oligomer by an esterification reaction of an aqueous solution containing bis-2-hydroxyethyl terephthalate purified by the purification method according to the present disclosure described above, a dicarboxylic acid or a derivative thereof, and a diol including ethylene glycol and a comonomer (Step 1); and

[0036] 2) producing a polyester copolymer by a polycondensation reaction of the oligomer (Step 2),

[0037] wherein the concentration of the aqueous solution containing bis-2-hydroxyethyl terephthalate is 25 wt% to 99 wt%.

[0038] Step 1 of the method for producing a polyester copolymer is a step of producing an oligomer by an esterification reaction of an aqueous solution containing bis-2-hydroxyethyl terephthalate, a dicarboxylic acid or a derivative thereof, and a diol including ethylene glycol and a comonomer.

[0039] The aqueous solution of bis-2-hydroxyethyl terephthalate can be an aqueous solution of bis-2-hydroxyethyl terephthalate purified by the purification method according to the present disclosure described above, or an aqueous solution in which bis-2-hydroxyethyl terephthalate crystals purified by the purification method according to the present disclosure are dissolved in water.

[0040] Preferably, the concentration of the aqueous solution including bis-2-hydroxyethyl terephthalate can be 25 wt% to 99 wt%. When the concentration is less than 25 wt%, the reaction efficiency is reduced due to the low concentration of bis-2-hydroxyethyl terephthalate. When the concentration exceeds 99 wt%, it is difficult to induce a uniform esterification reaction due to the high concentration of bis-2-hydroxyethyl terephthalate.

[0041] In addition, the temperature of the aqueous solution including bis-2-hydroxyethyl terephthalate can preferably be 25°C to 100°C, and more preferably 30°C to 90°C.

[0042] Meanwhile, the dicarboxylic acid or derivative thereof for the present disclosure refers to a main monomer constituting a polyester copolymer together with a diol component. In particular, the dicarboxylic acid includes terephthalic acid, and the physical properties of the polyester copolymer according to the present disclosure such as heat resistance, chemical resistance, and weather resistance can be improved by terephthalic acid. In addition, the terephthalic acid derivative can be terephthalic acid alkyl ester, preferably dimethyl terephthalate.

[0043] In addition to terephthalic acid, the dicarboxylic acid can include an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or a mixture thereof. In this case, the dicarboxylic acid other than terephthalic acid is preferably included in 1 wt% to 30 wt% based on the total weight of the total dicarboxylic acid component.

[0044] The aromatic dicarboxylic acid component can be an aromatic dicarboxylic acid having 8 to 20 carbon atoms, preferably 8 to 14 carbon atoms, or a mixture thereof. Specific examples of the aromatic dicarboxylic acid include isophthalic acid, naphthalene dicarboxylic acid such as 2,6-naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, 4,4'-stilbene dicarboxylic acid, 2,5-furan dicarboxylic acid, 2,5-thiophene dicarboxylic acid, and the like, but are not limited thereto. The aliphatic dicarboxylic acid component can be an aliphatic dicarboxylic acid component having 4 to 20 carbon atoms, preferably 4 to 12 carbon atoms, or a mixture thereof. Specific examples of the aliphatic dicarboxylic acid include linear, branched, or cyclic aliphatic dicarboxylic acid components, including cyclohexane dicarboxylic acid such as 1,4-cyclohexane dicarboxylic acid and 1,3-cyclohexane dicarboxylic acid, phthalic acid, sebacic acid, succinic acid, isodecyl succinic acid, maleic acid, fumaric acid, adipic acid, glutaric acid, and azelaic acid, but are not limited thereto.

[0045] The diol component for the present disclosure refers to a main monomer constituting a polyester copolymer together with the above-described dicarboxylic acid or derivative thereof. In particular, the diol component includes ethylene glycol and a comonomer, and the comonomer includes cyclohexanedimethanol, isosorbide, or diethylene glycol.

[0046] Ethylene glycol is a component that helps improve the transparency and impact strength of the polyester copolymer. Preferably, ethylene glycol can be used in an amount of 5 moles to 100 moles based on 100 moles of the total diol component.

[0047] Cyclohexanedimethanol (e.g., 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, or 1,4-cyclohexanedimethanol) is a component that helps improve the transparency and impact strength of the polyester copolymer to be prepared. Preferably, cyclohexanedimethanol can be used in an amount of 5 moles to 90 moles based on 100 moles of the total diol component.

[0048] Isosorbide is used to improve the processability of the polyester copolymer to be prepared. Although the diols of cyclohexanedimethanol and ethylene glycol improve the transparency and impact resistance of the polyester copolymer, in order to improve the processability, the shear thinning property should be improved and the crystallization rate should be reduced. However, it is difficult to achieve these effects using only cyclohexanedimethanol and ethylene glycol. When isosorbide is included as a diol component, the shear thinning property is improved and the crystallization rate is reduced while maintaining the transparency and impact strength, thereby improving the processability of the polyester copolymer to be prepared. Preferably, isosorbide can be used in an amount of 0.1 moles to 50 moles based on 100 moles of the total diol component.

[0049] Meanwhile, as will be described later, the polyester copolymer prepared according to the present disclosure includes 1 wt% to 90 wt% of residues of bis-2-hydroxyethyl terephthalate. To this end, the concentration of the recycled bis-2-hydroxyethyl terephthalate solution prepared in Step 1 is adjusted as described above. When the residues of recycled bis-2-hydroxyethyl terephthalate are less than 1 wt%, the content of the above-mentioned diols is relatively high, and thus more by-products derived from the diol component, particularly, ethylene glycol, are produced, resulting in deterioration of the quality of the polyester copolymer. In addition, when the residues of recycled bis-2-hydroxyethyl terephthalate are greater than 90 wt%, there is a problem of deterioration of the color quality and transparency of the polyester copolymer.

[0050] The esterification reaction can be performed at 0.1 kg / cm 2 to 3.0 kg / cm 2The esterification reaction can be performed at a temperature of 200°C to 300°C and a pressure of 400 mmHg to 0.01 mmHg. The conditions of the esterification reaction can be appropriately adjusted according to the specific properties of the polyester to be prepared, the ratio of each component, or the process conditions. Specifically, the temperature of the esterification reaction can be 240°C to 295°C, more preferably 245°C to 275°C.

[0051] The esterification reaction can be performed in a batch or continuous manner. The respective raw materials can be added separately, or the respective raw materials can be added in the form of a slurry by mixing the diol component with the dicarboxylic acid component and the recycled bis-2-hydroxyethyl terephthalate solution. In addition, the diol component, such as isosorbide, which is a solid component at room temperature, can be dissolved in water or ethylene glycol, and then mixed with the dicarboxylic acid component, such as terephthalic acid, to form a slurry. Alternatively, after isosorbide is melted at 60°C or higher, the slurry can be prepared by mixing the dicarboxylic acid component, such as terephthalic acid, and the other diol component with isosorbide. In addition, water can be added to the mixed slurry to help increase the flowability of the slurry.

[0052] Preferably, the esterification reaction of step 2 is performed for 2 hours to 10 hours. The reaction time affects the quality of the polyester copolymer finally prepared, and when the reaction time is less than 2 hours or more than 10 hours, the color quality of the polyester copolymer finally prepared deteriorates.

[0053] Meanwhile, the esterification reaction can use a catalyst including a titanium-based compound, a germanium-based compound, an antimony-based compound, an aluminum-based compound, a tin-based compound, or a mixture thereof.

[0054] Examples of the titanium-based compound can include tetraethyl titanate, acetyl tripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, octyleneglycol titanate, lactic acid titanate, triethanolamine titanate, acetyl acetonate titanate, ethyl acetoacetate titanate, isostearyl titanate, titanium dioxide, and the like. Examples of the germanium-based compound can include germanium dioxide, germanium tetrachloride, ethylene glycol germanium, germanium acetate, copolymers thereof, and mixtures thereof. Preferably, germanium dioxide can be used, and the germanium dioxide can be in a crystalline form or an amorphous form. Diol-soluble germanium dioxide can also be used.

[0055] Step 2 of the method for preparing a polyester copolymer is a step of preparing a polyester copolymer through a polycondensation reaction of the oligomer.

[0056] The polycondensation reaction can be performed by reacting the esterification product at a temperature of 240°C to 300°C and a pressure of 400 mmHg to 0.01 mmHg. In addition, the polycondensation reaction can be performed for 1 hour to 10 hours.

[0057] The temperature condition and the pressure condition of the polycondensation reaction enable diols, which are by-products of the polycondensation reaction, to be removed from the system. In addition, when the polycondensation reaction is performed within the reaction time described above, the intrinsic viscosity of the final product can reach a suitable level.

[0058] In addition, a polyester copolymer prepared according to the method for preparing a polyester copolymer described above is provided.

[0059] Meanwhile, the polyester copolymer according to the present disclosure can have an intrinsic viscosity of 0.50 dl / g to 1.0 dl / g, preferably 0.50 dl / g to 0.85 dl / g, and more preferably 0.55 dl / g to 0.80 dl / g. The method for measuring the intrinsic viscosity will be described in detail in the examples to be described later.

[0060] In addition, '(Hunter L value) - (Hunter b value)' (hereinafter, referred to as Plaque Color L-b) measured with respect to a 6 mm thick sample of the polyester copolymer according to the present disclosure can be 87 or more, and more preferably 88 or more, 89 or more, or 90 or more. In addition, the upper limit of the Plaque Color L-b can be 100, and in the present disclosure, the Plaque Color L-b can be 99 or less, 98 or less, 97 or less, 96 or less, or 95 or less. The method for measuring the Plaque Color L-b will be described in detail in the examples to be described later.

[0061] In addition, the haze measured with respect to a 6 mm thick sample of the polyester copolymer according to the present disclosure can be 3 or less, and more preferably 2.5 or less. In addition, the upper limit of the haze can be 0, and in the present disclosure, the haze can be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, or 0.5 or more. The method for measuring the haze will be described in detail in the examples to be described later.

[0062] In the present disclosure, a product including the polyester copolymer is also provided.

[0063] Advantageous effects

[0064] As described above, the purification method according to the present disclosure can purify bis-2-hydroxyethyl terephthalate at a high purity, and using the bis-2-hydroxyethyl terephthalate as a monomer of a polyester copolymer allows good color quality. DETAILED DESCRIPTION

[0065] Hereinafter, preferred examples are provided to help the understanding of the present invention. However, the following examples are provided only to make the present invention easier to understand, and the present invention is not limited thereto.

[0066] Bis-2-hydroxyethyl terephthalate (BHET) having a commercial quality was used, and was used in the following preparation examples, examples, and comparative examples.

[0067] Preparation Example

[0068] Preparation Example 1: Purification of BHET using distilled water and activated carbon

[0069] To a 20 L container, 1250 g of distilled water was added, and then heated at 70°C under stirring. When the temperature reached 70°C, 250 g of BHET was added and completely dissolved. When the BHET was completely dissolved, 0.5 wt% of powdered activated carbon was added based on the added BHET, followed by stirring for 1 hour to adsorb impurities. Thereafter, the undissolved impurities and activated carbon were removed through a heated filter. The BHET aqueous solution passing through the filter was cooled to room temperature (23°C) to obtain crystallized BHET, which was separated from the mixed solution by a filter, and dried under reduced pressure to finally obtain purified BHET.

[0070] Preparation Example 2: Purification of BHET using activated carbon and use in a polymerization process in an aqueous solution state

[0071] To a 3 L container, 300 g of distilled water was added, and then heated at 85°C under stirring. When the temperature reached 85°C, 2000 g of BHET was slowly added and completely dissolved. When the BHET was completely dissolved, 0.5 wt% of powdered activated carbon was added based on the added BHET, followed by stirring for 1 hour to adsorb impurities. Thereafter, the undissolved impurities and activated carbon were removed through a heated filter.

[0072] Comparative Preparation Example 1: Purification of BHET using distilled water

[0073] BHET was obtained in the same manner as in Preparation Example 1, except that the adsorption purification using activated carbon in Preparation Example 1 was not performed.

[0074] Comparative Preparation Example 2: Unpurified BHET aqueous solution

[0075] An aqueous solution of BHET dissolved in the same composition as in Preparation Example 2 was prepared without separate purification.

[0076] Comparative Preparation Example 3: Unpurified BHET

[0077] BHET crystals that were not separately purified and mixed with distilled water were prepared.

[0078] The purity, color, and yield of the BHET obtained in the preparation examples and the comparative preparation examples were measured, and are shown in Table 1 below. At this time, the color of each crystal was measured, and was measured with a spectrophotometer (CM-3600A) from Konica Minolta.

[0079] Table 1

[0080]

[0081] Example

[0082] Example 1

[0083] A 3L container was added with 200 g of distilled water, and then heated at 85℃ under stirring. When the temperature reached 85℃, 1269.7 g of BHET was slowly added and completely dissolved. When the BHET was completely dissolved, 0.5 wt% of powdered activated carbon was added based on the added BHET, followed by stirring for 1 hour to adsorb impurities. Thereafter, the undissolved impurities and activated carbon were removed through a heated filter to prepare a BHET solution (concentration: 86.4%).

[0084] The BHET solution prepared above, TPA (terephthalic acid; 2361.8 g), EG (ethylene glycol; 673.5 g), CHDM (1,4-cyclohexanedimethanol; 221.5 g), and ISB (isosorbide; 98.2 g) were placed in a 10L reactor, a column and a condenser capable of being cooled by water were connected to the reactor, and GeO2 (1.0 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, and cobalt acetate (0.7 g) as a colorant were added to the reactor.

[0085] Then, nitrogen was injected into the reactor to form a pressurized state in which the pressure of the reactor was higher than normal pressure by 1.0 kgf / cm 2 (abs. pressure: 1495.6 mmHg). Then, the temperature of the reactor was increased to 220℃ over 90 minutes, maintained at 220℃ for 2 hours, and then increased to 260℃ over 2 hours. Thereafter, the esterification reaction was performed while maintaining the temperature of the reactor at 260℃ for 245 minutes until the mixture in the reactor became transparent to the naked eye. In this process, a byproduct flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to normal pressure, and then the mixture in the reactor was transferred to a 7L reactor capable of performing a vacuum reaction.

[0086] Then, the pressure of the reactor was decreased from the normal pressure to 5 torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 280°C over 1 hour to perform the polycondensation reaction while the pressure of the reactor was maintained at 1 torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants rose above the set temperature, the stirring rate could be appropriately adjusted. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.55 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg.

[0087] The pellets were allowed to stand at 150°C for 1 hour to crystallize, and then the pellets were placed into a 20 L solid phase polymerization reactor. Then, nitrogen was flowed into the reactor at a rate of 50 L / min. Here, the temperature of the reactor was increased from room temperature to 140°C at a rate of 40°C / hour, and maintained at 140°C for 3 hours. Thereafter, the temperature was further increased to 200°C at a rate of 40°C / hour, and maintained at 200°C. The solid phase polymerization reaction was performed until the intrinsic viscosity (IV) of the pellets in the reactor reached 0.70 dl / g to prepare a polyester copolymer.

[0088] Example 2

[0089] An aqueous solution of r-BHET was prepared by dissolving r-BHET (3461.1 g) prepared in Preparation Example 1 in water (200 g) at 70°C.

[0090] The aqueous solution of r-BHET prepared above, TPA (969.4 g), EG (12.1 g), CHDM (140.2 g), and ISB (113.7 g) were placed in a 10 L reactor, a column and a condenser capable of being cooled by water were connected to the reactor, and GeO2 (1.0 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, and cobalt acetate (0.7 g) as a colorant were added to the reactor.

[0091] Then, nitrogen was injected into the reactor to form a pressurized state in which the pressure of the reactor was 1.0 kgf / cm2 higher than the normal pressure. 2(abs. pressure: 1495.6 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 260°C over 2 hours. Thereafter, the esterification reaction was performed while maintaining the temperature of the reactor at 260°C for 200 minutes until the mixture in the reactor became transparent to the naked eye. During this process, a by-product flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to normal pressure, and then the mixture in the reactor was transferred to a 7L reactor capable of performing a vacuum reaction.

[0092] Then, the pressure of the reactor was reduced from normal pressure to 5 torr (abs. pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 280°C over 1 hour to perform a polycondensation reaction while maintaining the pressure of the reactor at 1 torr (abs. pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants rose above the set temperature, the stirring rate could be adjusted as appropriate. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.60 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg.

[0093] The pellets were allowed to stand at 150°C for 1 hour to crystallize, and then the pellets were placed into a 20L solid phase polymerization reactor. Then, nitrogen was caused to flow into the reactor at a rate of 50 L / min. Here, the temperature of the reactor was increased from room temperature to 140°C at a rate of 40°C / hour, and maintained at 140°C for 3 hours. Thereafter, the temperature was further increased to 200°C at a rate of 40°C / hour, and maintained at 200°C. The solid phase polymerization reaction was performed until the intrinsic viscosity (IV) of the pellets in the reactor reached 0.95 dl / g to produce a polyester copolymer.

[0094] Example 3

[0095] To a 3L container, 200g of distilled water was added, and then heated at 85°C with stirring. When the temperature reached 85°C, 3461.1g of BHET was slowly added and completely dissolved. When the BHET was completely dissolved, 0.5wt% of powdered activated carbon was added based on the added BHET, followed by stirring for 1 hour to adsorb impurities. Thereafter, the undissolved impurities and activated carbon were removed by a heated filter to prepare a BHET solution (concentration: 94.5%).

[0096] The BHET solution prepared above, TPA (420.3 g), EG (39.2 g), and CHDM (121.5 g) were placed in a 10 L reactor to which a column and a condenser capable of being cooled by water were attached, and to the reactor was added Ti02 / Si02copolymer (0.5 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, Polysynthren Blue RLS (manufactured by Clarient, 0.016 g) as a blue toner, and Solvaperm Red BB (manufactured by Clarient, 0.004 g) as a red toner.

[0097] Then, nitrogen was injected into the reactor to form a pressurized state in which the pressure of the reactor was 0.5 kgf / cm2higher than the normal pressure (absolute pressure: 1127.8 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 260°C over 2 hours. Thereafter, the esterification reaction was performed while the temperature of the reactor was maintained at 260°C for 500 minutes until the mixture in the reactor became transparent to the naked eye. In this process, the byproduct flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to the normal pressure, and then the mixture in the reactor was transferred to a 7 L reactor capable of performing a vacuum reaction. 2 (absolute pressure: 1127.8 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 260°C over 2 hours. Thereafter, the esterification reaction was performed while the temperature of the reactor was maintained at 260°C for 500 minutes until the mixture in the reactor became transparent to the naked eye. In this process, the byproduct flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to the normal pressure, and then the mixture in the reactor was transferred to a 7 L reactor capable of performing a vacuum reaction.

[0098] Then, the pressure of the reactor was reduced from the normal pressure to 5 torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 275°C over 1 hour to perform the polycondensation reaction while the pressure of the reactor was maintained at 1 torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants increased above the set temperature, the stirring rate could be adjusted as appropriate. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.60 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 mg to 14 mg.

[0099] The particles were allowed to stand at 150°C for 1 hour to crystallize, and then placed into a 20L solid-phase polymerization reactor. Nitrogen gas was then introduced into the reactor at a rate of 50L / min. The reactor temperature was then increased from room temperature to 140°C at a rate of 40°C / hour and maintained at 140°C for 3 hours. Subsequently, the temperature was further increased to 210°C at a rate of 40°C / hour and maintained at 210°C. Solid-phase polymerization was carried out until the intrinsic viscosity (IV) of the particles in the reactor reached 0.80 dl / g to prepare the polyester copolymer.

[0100] Example 4

[0101] The r-BHET (795.8 g), TPA (3814.0 g), EG (1554.0 g), and CHDM (188.0 g) prepared in Preparation Example 1 were placed in a 10 L reactor. A column and a water-coolable condenser were connected to the reactor. TiO2 / SiO2 copolymer (0.5 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, and cobalt acetate (1.1 g) as a colorant were added to the reactor.

[0102] Then, nitrogen gas is injected into the reactor to create a pressurized environment, wherein the reactor pressure is 1.0 kgf / cm² higher than atmospheric pressure. 2 (Absolute pressure: 1495.6 mmHg). The reactor temperature was then raised to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then raised to 250°C over another 2 hours. Subsequently, the esterification reaction was carried out for 500 minutes while maintaining the reactor temperature at 250°C, until the mixture in the reactor became transparent to the naked eye. During this process, byproducts flowed through a column and a condenser. When the esterification reaction was complete, the nitrogen gas in the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure, and the mixture in the reactor was then transferred to a 7L reactor capable of vacuum reaction.

[0103] Then, the pressure of the reactor was decreased from normal pressure to 5 torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 265°C over 1 hour to perform the polycondensation reaction while the pressure of the reactor was maintained at 1 torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants increased above the set temperature, the stirring rate could be appropriately adjusted. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.55 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg.

[0104] The pellets were allowed to stand at 150°C for 1 hour to crystallize, and then the pellets were placed into a 20 L solid phase polymerization reactor. Then, nitrogen was flowed into the reactor at a rate of 50 L / min. Here, the temperature of the reactor was increased from room temperature to 140°C at a rate of 40°C / hour, and maintained at 140°C for 3 hours. Thereafter, the temperature was further increased to 220°C at a rate of 40°C / hour, and maintained at 220°C. The solid phase polymerization reaction was performed until the intrinsic viscosity (IV) of the pellets in the reactor reached 0.85 dl / g to prepare a polyester copolymer.

[0105] Example 5

[0106] To a 3 L container, 300 g of distilled water was added, and then heated at 85°C with stirring. When the temperature reached 85°C, 2439.2 g of BHET was slowly added and completely dissolved. When the BHET was completely dissolved, 0.5 wt% of powdered activated carbon was added based on the added BHET, followed by stirring for 1 hour to adsorb impurities. Thereafter, the undissolved impurities and activated carbon were removed through a heated filter to prepare a BHET solution (concentration: 89.0%).

[0107] The BHET solution prepared above, TPA (1471.5 g), EG (68.7 g), and CHDM (797.8 g) were placed in a 10 L reactor, a column and a condenser capable of being cooled by water were connected to the reactor, and to the reactor was added TiO2 / SiO2 copolymer (1.0 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, and cobalt acetate (0.8 g) as a colorant.

[0108] Then, nitrogen was injected into the reactor to form a pressurized state in which the pressure of the reactor was 2.0 kgf / cm2 higher than normal pressure. 2(absolute pressure: 2231.1 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 255°C over 2 hours. Thereafter, the esterification reaction was performed while maintaining the temperature of the reactor at 255°C for 360 minutes until the mixture in the reactor became transparent to the naked eye. During this process, a by-product flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to normal pressure, and then the mixture in the reactor was transferred to a 7L reactor capable of performing a vacuum reaction.

[0109] Then, the pressure of the reactor was reduced from normal pressure to 5 torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 285°C over 1 hour to perform the polycondensation reaction while maintaining the pressure of the reactor at 1 torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants rose above the set temperature, the stirring rate could be adjusted as appropriate. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.70 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg to prepare a polyester copolymer.

[0110] Example 6

[0111] The r-BHET (40.9 g) prepared above, TPA (2643.1 g), EG (329.1 g), CHDM (1158.0 g), and ISB (587.0 g) were placed in a 10L reactor, a column and a condenser capable of being cooled by water were connected to the reactor, and GeO2 (1.0 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, Polysynthren Blue RLS (manufactured by Clarient, 0.020 g) as a blue toner, and Solvaperm Red BB (manufactured by Clarient, 0.008 g) as a red toner were added to the reactor.

[0112] Then, nitrogen was injected into the reactor to form a pressurized state in which the pressure of the reactor was 0.5 kgf / cm 2(abs. pressure: 1127.8 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 260°C over 2 hours. Thereafter, the esterification reaction was performed while maintaining the temperature of the reactor at 260°C for 360 minutes until the mixture in the reactor became transparent to the naked eye. During this process, a by-product flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to normal pressure, and then the mixture in the reactor was transferred to a 7L reactor capable of performing a vacuum reaction.

[0113] Then, the pressure of the reactor was reduced from normal pressure to 5 torr (abs. pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 275°C over 1 hour to perform the polycondensation reaction while maintaining the pressure of the reactor at 1 torr (abs. pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants rose above the set temperature, the stirring rate could be adjusted as appropriate. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.80 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg to prepare a polyester copolymer.

[0114] Example 7

[0115] To a 3L container, 100 g of distilled water was added, and then heated at 85°C with stirring. When the temperature reached 85°C, 3418.5 g of BHET was slowly added and completely dissolved. When the BHET was completely dissolved, 0.5 wt% of powdered activated carbon was added based on the added BHET, followed by stirring for 1 hour to adsorb impurities. Thereafter, the undissolved impurities and activated carbon were removed by a heated filter to prepare a BHET solution (concentration: 97.2%).

[0116] The r-BHET solution prepared above, TPA (957.5 g), DMT (dimethyl terephthalate; 1119.0 g), EG (345.7 g), CHDM (221.5 g), and ISB (84.2 g) were placed in a 10L reactor to which a column and a condenser capable of being cooled by water were connected, and to the reactor was added manganese (II) acetate tetrahydrate (1.5 g) and Sb203 (1.8 g) as catalysts and cobalt acetate (0.7 g) as a colorant.

[0117] Then, nitrogen was injected into the reactor to bring the pressure of the reactor to normal pressure. Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 240°C over 2 hours. Thereafter, the esterification reaction was performed while maintaining the temperature of the reactor at 240°C for 150 minutes until the mixture in the reactor became transparent to the naked eye. In this process, a by-product flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to normal pressure, and then the mixture in the reactor was transferred to a 7L reactor capable of performing a vacuum reaction.

[0118] Then, the pressure of the reactor was reduced from normal pressure to 5 torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 265°C over 1 hour to perform a polycondensation reaction while maintaining the pressure of the reactor at 1 torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants increased above the set temperature, the stirring rate could be appropriately adjusted. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.60 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg.

[0119] The pellets were allowed to stand at 150°C for 1 hour to crystallize, and then the pellets were placed into a 20L solid phase polymerization reactor. Then, nitrogen was flowed into the reactor at a rate of 50 L / min. Here, the temperature of the reactor was increased from room temperature to 140°C at a rate of 40°C / hour, and maintained at 140°C for 3 hours. Thereafter, the temperature was further increased to 200°C at a rate of 40°C / hour, and maintained at 200°C. The solid phase polymerization reaction was performed until the intrinsic viscosity (IV) of the pellets in the reactor reached 0.95 dl / g to prepare a polyester copolymer.

[0120] Example 8

[0121] An aqueous solution of r-BHET was prepared by dissolving r-BHET (3461.1 g) prepared in Preparation Example 1 in water (1500 g) at 95°C.

[0122] An aqueous solution of r-BHET prepared above, TPA (969.4 g), IPA (isophthalic acid; 2262.0 g), EG (12.1 g), CHDM (140.2 g), and ISB (113.7 g) were placed in a 10 L reactor, a column and a condenser capable of being cooled by water were attached to the reactor, and GeO2 (1.0 g) as a catalyst and cobalt acetate (0.7 g) as a colorant were added to the reactor.

[0123] Then, nitrogen was injected into the reactor to form a pressurized state in which the pressure of the reactor was 3.0 kgf / cm2 higher than the normal pressure 2 (abs. pressure: 2956.7 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 260°C over 2 hours. Thereafter, the esterification reaction was performed while the temperature of the reactor was maintained at 260°C for 200 minutes until the mixture in the reactor became transparent to the naked eye. In this process, a by-product flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to the normal pressure, and then the mixture in the reactor was transferred to a 7 L reactor capable of performing a vacuum reaction.

[0124] Then, the pressure of the 7 L reactor was reduced from the normal pressure to 5 torr (abs. pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 280°C over 1 hour to perform a polycondensation reaction while the pressure of the reactor was maintained at 1 torr (abs. pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants rose above the set temperature, the stirring rate could be adjusted as appropriate. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.60 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg.

[0125] The pellets were allowed to stand at 150°C for 1 hour to crystallize, and then the pellets were placed into a 20 L solid phase polymerization reactor. Then, nitrogen was caused to flow into the reactor at a rate of 50 L / min. Here, the temperature of the reactor was increased from room temperature to 140°C at a rate of 40°C / hour, and maintained at 140°C for 3 hours. Thereafter, the temperature was further increased to 190°C at a rate of 40°C / hour, and maintained at 190°C. The solid phase polymerization reaction was performed until the intrinsic viscosity (IV) of the pellets in the reactor reached 1.0 dl / g to prepare a polyester copolymer.

[0126] Comparative Example 1

[0127] The r-BHET (1291.0 g), TPA (2401.4 g), EG (721.2 g), CHDM (140.8 g), and ISB (99.9 g) of Comparative Preparation Example 3 were placed in a 10 L reactor. A column and a water-coolable condenser were connected to the reactor, and GeO2 (1.0 g) as a catalyst and phosphoric acid (1.46 g) as a stabilizer were added to the reactor.

[0128] Then, nitrogen gas is injected into the reactor to create a pressurized environment, wherein the pressure in the reactor is 0.5 kgf / cm² higher than atmospheric pressure. 2 (Absolute pressure: 1127.8 mmHg). The reactor temperature was then raised to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then raised to 260°C over another 2 hours. Subsequently, the esterification reaction was carried out for 720 minutes while maintaining the reactor temperature at 260°C, until the mixture in the reactor became transparent to the naked eye. During this process, byproducts flowed through a column and a condenser. When the esterification reaction was complete, the nitrogen gas in the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure, and the mixture in the reactor was then transferred to a 7L reactor capable of vacuum reaction.

[0129] Then, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) over 30 minutes, and the reactor temperature is increased to 280°C over 1 hour to initiate the polycondensation reaction, while the reactor pressure is maintained at 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate is set to high, but can be adjusted appropriately as the stirring force decreases due to the increased viscosity of the reactants during the polycondensation reaction, or as the temperature of the reactants rises above the set temperature. The polycondensation reaction continues until the intrinsic viscosity (IV) of the mixture (melt) in the reactor becomes 0.60 dl / g. When the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor and formed into a filament. It is then solidified with a coolant and granulated to have an average weight of approximately 12 mg to 14 mg.

[0130] The particles were allowed to stand at 150°C for 1 hour to crystallize, and then placed into a 20L solid-phase polymerization reactor. Nitrogen gas was then introduced into the reactor at a rate of 50L / min. The reactor temperature was then increased from room temperature to 140°C at a rate of 40°C / hour and maintained at 140°C for 3 hours. Subsequently, the temperature was further increased to 200°C at a rate of 40°C / hour and maintained at 200°C. Solid-phase polymerization was carried out until the intrinsic viscosity (IV) of the particles in the reactor reached 0.70 dl / g to prepare the polyester copolymer.

[0131] Comparative Example 2

[0132] The r-BHET (304.1 g), TPA (2640.8 g), EG (583.3 g), CHDM (1231.6 g), and ISB (25.0 g) prepared in Comparative Preparation Example 1 were placed in a 10 L reactor. A column and a water-coolable condenser were connected to the reactor. GeO2 (1.0 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, Polysynthren Blue RLS (manufactured by Clarient, 0.012 g) as a blue toner, and Solvaperm Red BB (manufactured by Clarient, 0.004 g) as a red toner were added to the reactor.

[0133] Then, nitrogen gas is injected into the reactor to create a pressurized environment, wherein the pressure in the reactor is 0.5 kgf / cm² higher than atmospheric pressure. 2 (Absolute pressure: 1127.8 mmHg). The reactor temperature was then raised to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then raised to 255°C over another 2 hours. Subsequently, the esterification reaction was carried out for 750 minutes while maintaining the reactor temperature at 255°C, until the mixture in the reactor became transparent to the naked eye. During this process, byproducts flowed through a column and a condenser. When the esterification reaction was complete, the nitrogen gas in the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure, and the mixture in the reactor was then transferred to a 7L reactor capable of vacuum reaction.

[0134] Then, the reactor pressure was reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) over 30 minutes, and the reactor temperature was increased to 280°C over 1 hour to carry out the polycondensation reaction, while the reactor pressure was maintained at 1 Torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but it could be adjusted appropriately as the stirring force decreased due to the increase in reactant viscosity as the polycondensation reaction proceeded, or as the reactant temperature rose above the set temperature. The polycondensation reaction continued until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.75 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and formed into a filament. This filament was then cured with a coolant and granulated to an average weight of approximately 12 mg to 14 mg to prepare the polyester copolymer.

[0135] Comparative Example 3

[0136] The r-BHET (3898.7 g), TPA (162.6 g), EG (81.0 g), and ISB (95.4 g) prepared in Preparation Example 1 were placed in a 10 L reactor. A column and a water-coolable condenser were connected to the reactor. GeO2 (1.0 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, Polysynthren Blue RLS (manufactured by Clarient, 0.010 g) as a blue toner, and Solvaperm RedBB (manufactured by Clarient, 0.003 g) as a red toner were added to the reactor.

[0137] Then, nitrogen gas is injected into the reactor to create a pressurized environment, wherein the pressure in the reactor is 0.1 kgf / cm² higher than atmospheric pressure. 2 (Absolute pressure: 823.6 mmHg). The reactor temperature was then raised to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then raised to 260°C over another 2 hours. Subsequently, the esterification reaction was carried out for 850 minutes while maintaining the reactor temperature at 260°C, until the mixture in the reactor became transparent to the naked eye. During this process, byproducts flowed through a column and a condenser. When the esterification reaction was complete, the nitrogen gas in the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure, and the mixture in the reactor was then transferred to a 7L reactor capable of vacuum reaction.

[0138] Then, the pressure of the reactor was decreased from normal pressure to 5 torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 270°C over 1 hour to perform the polycondensation reaction while the pressure of the reactor was maintained at 1 torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants increased to be higher than the set temperature, the stirring rate could be appropriately adjusted. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.65 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg.

[0139] The pellets were allowed to stand at 150°C for 1 hour to crystallize, and then the pellets were placed into a 20 L solid phase polymerization reactor. Then, nitrogen was flowed into the reactor at a rate of 50 L / min. Here, the temperature of the reactor was increased from room temperature to 140°C at a rate of 40°C / hour, and maintained at 140°C for 3 hours. Thereafter, the temperature was further increased to 220°C at a rate of 40°C / hour, and maintained at 220°C. The solid phase polymerization reaction was performed until the intrinsic viscosity (IV) of the pellets in the reactor reached 0.85 dl / g to prepare a polyester copolymer.

[0140] Comparative Example 4

[0141] To a 3 L container, 2300 g of distilled water was added, and then heated at 85°C with stirring. When the temperature reached 85°C, 735.6 g of BHET was slowly added and completely dissolved to prepare a BHET solution (concentration: 24.2%).

[0142] The BHET solution prepared above, TPA (2724.3 g), EG (1239.0 g), CHDM (222.4 g), and ISB (98.7 g) were placed in a 10 L reactor, a column and a condenser capable of being cooled by water were connected to the reactor, and GeO2 (1.0 g) as a catalyst and phosphoric acid (1.46 g) as a stabilizer were added to the reactor.

[0143] Then, nitrogen was injected into the reactor to form a pressurized state in which the pressure of the reactor was 0.5 kgf / cm 2(abs. pressure: 1127.8 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 260°C over 2 hours. Thereafter, the esterification reaction was performed while maintaining the temperature of the reactor at 260°C for 650 minutes until the mixture in the reactor became transparent to the naked eye. During this process, a by-product flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to normal pressure, and then the mixture in the reactor was transferred to a 7L reactor capable of performing a vacuum reaction.

[0144] Then, the pressure of the reactor was reduced from normal pressure to 5 torr (abs. pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 280°C over 1 hour to perform the polycondensation reaction while maintaining the pressure of the reactor at 1 torr (abs. pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants rose above the set temperature, the stirring rate could be adjusted as appropriate. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.60 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg.

[0145] The pellets were allowed to stand at 150°C for 1 hour to crystallize, and then the pellets were placed into a 20L solid phase polymerization reactor. Then, nitrogen was caused to flow into the reactor at a rate of 50 L / min. Here, the temperature of the reactor was increased from room temperature to 140°C at a rate of 40°C / hour, and maintained at 140°C for 3 hours. Thereafter, the temperature was further increased to 200°C at a rate of 40°C / hour, and maintained at 200°C. The solid phase polymerization reaction was performed until the intrinsic viscosity (IV) of the pellets in the reactor reached 0.70 dl / g to produce a polyester copolymer.

[0146] Comparative Example 5

[0147] To a 3L container, 3000g of distilled water was added, and then heated at 85°C with stirring. When the temperature reached 85°C, 615.7g of BHET was slowly added and completely dissolved. When the BHET was completely dissolved, 0.5wt% of powdered activated carbon was added based on the added BHET, followed by stirring for 1 hour to adsorb impurities. Thereafter, the undissolved impurities and activated carbon were removed by a heated filter to prepare a BHET solution (concentration: 17.0%).

[0148] The BHET solution prepared above, TPA (2280.0 g), EG (566.0 g), CHDM (698.1 g), and ISB (82.6 g) were placed in a 10 L reactor to which a column and a condenser capable of being cooled by water were connected, and to the reactor was added GeO2(1.0 g) as a catalyst, phosphoric acid (1.46 g) as a stabilizer, and cobalt acetate (0.7 g) as a colorant.

[0149] Then, nitrogen was injected into the reactor to form a pressurized state in which the pressure of the reactor was 0.5 kgf / cm2higher than the normal pressure (absolute pressure: 1127.8 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 260°C over 2 hours. Thereafter, the esterification reaction was performed while the temperature of the reactor was maintained at 260°C for 900 minutes until the mixture in the reactor became transparent to the naked eye. In this process, the byproduct flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to the normal pressure, and then the mixture in the reactor was transferred to a 7 L reactor capable of performing a vacuum reaction. 2 (absolute pressure: 1127.8 mmHg). Then, the temperature of the reactor was increased to 220°C over 90 minutes, maintained at 220°C for 2 hours, and then increased to 260°C over 2 hours. Thereafter, the esterification reaction was performed while the temperature of the reactor was maintained at 260°C for 900 minutes until the mixture in the reactor became transparent to the naked eye. In this process, the byproduct flowed through the column and the condenser. When the esterification reaction was completed, the nitrogen in the pressurized reactor was discharged to the outside to reduce the pressure of the reactor to the normal pressure, and then the mixture in the reactor was transferred to a 7 L reactor capable of performing a vacuum reaction.

[0150] Then, the pressure of the reactor was reduced from the normal pressure to 5 torr (absolute pressure: 5 mmHg) over 30 minutes, and the temperature of the reactor was increased to 280°C over 1 hour to perform the polycondensation reaction while the pressure of the reactor was maintained at 1 torr (absolute pressure: 1 mmHg) or less. In the initial stage of the polycondensation reaction, the stirring rate was set to high, but when the stirring force was weakened due to an increase in the viscosity of the reactants as the polycondensation reaction proceeded, or the temperature of the reactants increased above the set temperature, the stirring rate could be adjusted as appropriate. The polycondensation reaction was performed until the intrinsic viscosity (IV) of the mixture (melt) in the reactor became 0.60 dl / g. When the intrinsic viscosity of the mixture in the reactor reached the desired level, the mixture was discharged from the reactor and made into strands. This was solidified with a cooling liquid and pelletized to have an average weight of about 12 to 14 mg to prepare a polyester copolymer.

[0151] Experimental Examples

[0152] The physical properties of the polyester copolymers prepared in the examples and comparative examples were evaluated as follows.

[0153] 1) Residual Composition

[0154] After dissolving the sample in a solvent of CDC13 at a concentration of 3 mg / mL, the residues consisting of acid and diol derived from the polyester resin (mol%) were confirmed by1H-NMR spectrum obtained at 25°C using a nuclear magnetic resonance apparatus (JEOL, 600 MHz FT-NMR). In addition, the residue of TMA was confirmed by quantitative analysis of the spectrum in which the content of benzene-1,2,4-triethylformate produced from the reaction of ethanol with TMA by ethanolysis was measured at 250°C using gas chromatography (Agilent Technologies, 7890B). And, it was confirmed as the content (wt%) based on the total weight of the polyester resin.

[0155] 2) Inherent viscosity

[0156] After dissolving the polyester copolymer in ortho-chlorophenol (OCP) at a concentration of 0.12% at 150°C, the inherent viscosity was measured using an Ubbelohde viscometer in a constant temperature bath at 35°C. Specifically, the temperature of the viscometer was maintained at 35°C, and the time taken by the solvent to pass between certain internal sections of the viscometer (flow-out time; t0) and the time taken by the solution to pass through the viscometer (t) were measured. Subsequently, the specific viscosity was calculated by substituting t0 and t into Equation 1, and the inherent viscosity was calculated by substituting the calculated specific viscosity into Equation 2.

[0157] [Equation 1]

[0158]

[0159] [Equation 2]

[0160]

[0161] 3) Substrate color L-b

[0162] The color and brightness of the sample were measured using a Varian Cary 5 UV / Vis / NIR spectrophotometer equipped with a diffuse reflectance accessory. A sample of the polyester resin having a thickness of 6 mm was prepared, and transmission data were obtained with a light source D65 at an observer angle of 2°. This was processed using the color analysis device in Grams / 32 software to calculate the Hunter L*a*b* values, and the result obtained by subtracting the b value from the L value (L-b) is described in the table below.

[0163] 4) Haze

[0164] A sample of the polyester resin having a thickness of 6 mm was prepared, and the haze of the sample was measured according to ASTM D1003-97 using a CM-3600A measuring instrument from Minolta.

[0165] The results are shown in Table 2 below.

[0166] Table 2

[0167]

[0168]

[0169] As shown in Table 2, the polyester copolymer prepared using the bis-2-hydroxyethyl terephthalate purified according to the present disclosure (Examples 1 to 8) has an excellent color L-b value of 87 or more. In another aspect, the polyester copolymer prepared using the bis-2-hydroxyethyl terephthalate prepared in Comparative Preparation Examples 1 to 3 (Comparative Examples 1, 2, and 4) and the polyester copolymer not using CHDM and ISB in polymerization (Comparative Examples 3 and 5) have a color L-b value lower than the above value.

[0170] Thus, it is confirmed that when the bis-2-hydroxyethyl terephthalate purified by the purification method according to the present disclosure is used as a monomer of a polyester resin, the polyester has excellent color quality.

Claims

1. A method for preparing polyester copolymers, comprising the following steps: 1) Mix bis-2-hydroxyethyl terephthalate and water; 2) Add activated carbon to the mixture from step 1); 3) Recover bis-2-hydroxyethyl terephthalate from the mixture in step 2). 4) An oligomer is prepared by esterification of an aqueous solution of bis-2-hydroxyethyl terephthalate obtained in step 3), a dicarboxylic acid or a derivative thereof, and a diol comprising ethylene glycol and a comonomer; and 5) A polyester copolymer is prepared by the polycondensation reaction of the oligomers. The concentration of the aqueous solution containing bis-2-hydroxyethyl terephthalate is from 25 wt% to 99 wt%. The dicarboxylic acid or its derivatives thereof are terephthalic acid, dimethyl terephthalate, isophthalic acid, 2,6-naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, 4,4'-stilbene dicarboxylic acid, 2,5-furan dicarboxylic acid or 2,5-thiophene dicarboxylic acid; The comonomer is cyclohexanediol, isosorbide, or diethylene glycol; The step 1) mentioned above is at 0.1 kg / cm 2 Up to 3.0 kg / cm 2 The pressure and temperature of 200°C to 300°C were applied; and The haze measured for a 6 mm thick sample of the polyester copolymer was 3 or less.

2. The method according to claim 1, wherein in step 1), the bis-2-hydroxyethyl terephthalate and water are mixed in a weight ratio of 1:100 to 99:

100.

3. The method according to claim 1, wherein in step 1), the temperature of the water is 50°C to 90°C.

4. The method according to claim 1, wherein in step 2), the activated carbon is added in an amount of 0.1 wt% to 5.0 wt% based on the weight of the mixture in step 1).

5. The method of claim 1, wherein step 3) is carried out by filtering the mixture of step 2) to recover the filtrate.

6. The method according to claim 5, wherein the filtrate is cooled to 10°C to 40°C to recover bis-2-hydroxyethyl terephthalate crystals.

7. The method according to claim 1, wherein the temperature of the aqueous solution containing bis-2-hydroxyethyl terephthalate is 25°C to 100°C.

8. The method of claim 1, wherein step 1) is performed for 2 to 10 hours.

9. The method of claim 1, wherein the polyester copolymer comprises 1 wt% to 90 wt% residues of bis-2-hydroxyethyl terephthalate.

10. The method according to claim 1, wherein the polyester copolymer has an intrinsic viscosity of 0.50 dl / g to 1.0 dl / g.

11. The method of claim 1, wherein the (Hunter L value) - (Hunter b value) value measured for a 6 mm thick sample of the polyester copolymer is 87 or greater.

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