Polyester copolymer comprising recycled monomers

Abstract

This invention relates to polyester copolymers containing recycled monomers, methods for their preparation, and articles thereof. The invention uses recycled monomers but can provide polyester copolymers with excellent properties, particularly polyester copolymers with excellent color properties and transparency.

Description

Technical Field

[0001] This invention relates to polyester copolymers containing recycled monomers, methods for their preparation, and articles containing the same. Prior Technology

[0002] Polyester possesses excellent mechanical strength, heat resistance, transparency, and gas barrier properties, making it ideally suited for use in beverage containers, packaging films, and audio-visual films, and it is widely used in these applications. Furthermore, it is extensively produced globally as an industrial material, such as medical fibers or tire cord fabrics and similar materials. Due to the good transparency and excellent mechanical strength of polyester sheets or boards, they are widely used as materials for boxes, cartons, shelves, protective panels, bubble wrap, building materials, and internal and external materials.

[0003] Meanwhile, waste plastics, which account for approximately 70% of marine pollution, have become a serious social problem. Countries around the world are regulating the use of disposable plastics and planning for their reuse. Methods for reusing waste plastics can be broadly categorized into two types: one involves collecting, grinding, and washing the waste plastics, followed by melt extrusion and regranulation, using this as a raw material; the other involves using materials obtained through the depolymerization of waste plastics as monomers for synthetic plastics. In the latter case, bis(2-hydroxyethyl) terephthalate can be obtained by depolymerizing PET or PETG from waste plastics, and used as a monomer for the polyester copolymer under study.

[0004] However, due to the impurities in waste plastics, it is difficult to obtain satisfactory materials, especially plastics made from materials obtained by depolymerization of waste plastics often suffer from quality deterioration.

[0005] Therefore, the inventors have demonstrated that by using recycled bis(2-hydroxyethyl) terephthalate as a monomer for polyester copolymers, but controlling the amount of other monomers as described later, the quality of polyester copolymers prepared from materials obtained by depolymerization of waste plastics can be improved, and the present invention is thus completed. Summary of the Invention

[0006] [Technical Issues]

[0007] The object of this invention is to provide a polyester copolymer comprising recycled monomers, a method for preparing the copolymer therefrom, and articles comprising the copolymer therefrom. [Technical Solution]

[0008] To achieve the purpose, a polyester copolymer polymerized from the following is provided. 1) Recovered bis(2-hydroxyethyl) terephthalate, 2) Acids containing dicarboxylic acids or their derivatives, and 3) Diols containing diethylene glycol and comonomers, and It has a structure in which the portions derived from bis(2-hydroxyethyl) terephthalate, the portions derived from dicarboxylic acids or their derivatives, and the portions derived from diols are repeated. The polyester copolymer comprises, in an amount of 5 to 70% by weight, the portion derived from recycled bis(2-hydroxyethyl) terephthalate, and The molar ratio of diol to dicarboxylic acid or its derivative is from 1.0:1 to 2.5:1. [Terminology Definition]

[0009] The copolymers of the present invention are copolymers prepared by copolymerization of dicarboxylic acid or its derivatives and diols comprising diethylene glycol and comonomers, wherein recycled bis(2-hydroxyethyl) terephthalate participates in the reaction during the copolymerization process.

[0010] The term "derivative" refers to a specific part or unit derived from a specific compound included in the chemical reaction products when that compound participates in a chemical reaction. Specifically, the acid moiety derived from dicarboxylic acids or their derivatives and the diol moiety derived from diols refer to repeating units of polyester copolymers formed by esterification or condensation polymerization, respectively. Furthermore, the moiety derived from bis(2-hydroxyethyl) terephthalate refers to repeating units of polyester copolymers formed by esterification in copolymerization. [Acids containing dicarboxylic acids or their derivatives]

[0011] As used herein, dicarboxylic acids or their derivatives refer to monomers that, together with diol components, constitute the main monomers of the polyester copolymer. In particular, dicarboxylic acids include terephthalic acid, and the properties of the polyester copolymers of the present invention can be improved by means of terephthalic acid. Furthermore, terephthalic acid residues can also be formed from alkyl esters of terephthalic acid (preferably dimethyl terephthalic acid).

[0012] In addition to terephthalic acid, the dicarboxylic acid component may further comprise an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component, or a mixture thereof. In this case, it is preferable that, in addition to terephthalic acid, it may comprise a dicarboxylic acid component in an amount of 1 to 30% by weight, based on the total weight of the total dicarboxylic acid components.

[0013] The aromatic dicarboxylic acid component may be C8-20, preferably C8-14, an aromatic dicarboxylic acid or a mixture thereof. Examples of aromatic dicarboxylic acids may include isophthalic acid, naphthalenedicarboxylic acid (e.g., 2,6-naphthalenedicarboxylic acid) and its analogues, diphenyl dicarboxylic acid, 4,4'-dinoflagic acid, 2,5-furanic acid, 2,5-thiophene dicarboxylic acid and its analogues, but specific examples of aromatic dicarboxylic acids are not limited thereto. The aliphatic dicarboxylic acid component may be C4-20, preferably C4-12, an aliphatic dicarboxylic acid or a mixture thereof. Examples of aliphatic dicarboxylic acids may include cyclohexanedicarboxylic acids (e.g., 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid and their analogues), linear, branched or cyclic aliphatic dicarboxylic acid components (e.g., phthalic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, fumaric acid, adipic acid, glutaric acid and azelaic acid and their analogues), but specific examples of aliphatic dicarboxylic acids are not limited to these.

[0014] Specifically, in addition to terephthalic acid, acids containing dicarboxylic acids or their derivatives may include one or more acids selected from the group consisting of isophthalic acid, dimethyl isophthalate, phthalic acid, dimethyl phthalate, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, dimethyl 2,6-naphthalenedicarboxylic acid, diphenyl dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, dimethyl 1,4-cyclohexanedicarboxylic acid, dimethyl 1,3-cyclohexanedicarboxylic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, glutaric acid, and azelaic acid. [Diol]

[0015] As used herein, the diol component refers to the main monomer that, together with the aforementioned dicarboxylic acid or its derivatives, constitutes the polyester copolymer. Specifically, the diol component comprises diethylene glycol and a comonomer, wherein the comonomer is ethylene glycol, cyclohexanediethanol, a cyclohexanediethanol derivative, or a combination thereof. Preferably, the cyclohexanediethanol derivative is 4-(hydroxymethyl)cyclohexanecarboxylic acid (4-(hydroxymethyl)cyclohexylmethyl) ester or 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylethanol. Preferably, in cases where the polyester resin of the present invention comprises a cyclohexanediethanol derivative, it may include a diol portion derived from 4-(hydroxymethyl)cyclohexanecarboxylic acid (4-(hydroxymethyl)cyclohexylmethyl) ester and 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylethanol in an amount of 0.1 to 25 mol%, based on the total diol portion.

[0016] Furthermore, preferably, as comonomers, 1,2-propanediol, 1,3-propanediol, 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, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, or mixtures thereof may be additionally included.

[0017] Diethylene glycol is a component that helps improve the color properties of polyester copolymers. Preferably, it may include 5 to 50 mol of diethylene glycol residues, based on 100 mol of total glycol component residues. More preferably, it may include 6 mol or more, 7 mol or more, or 8 mol or more, and 45 mol or less, 40 mol or less, 35 mol or less, 30 mol or less, 25 mol or less, or 20 mol or less, based on 100 mol of total glycol component residues.

[0018] Ethylene glycol is a component that helps improve the transparency and impact resistance of polyester copolymers. Preferably, it includes 30 to 80 moles of ethylene glycol residues, based on 100 moles of total glycol component residues. More preferably, it includes 35 moles or more, 40 moles or more, 45 moles or more, 50 moles or more, or 55 moles or more, and 75 moles or less of ethylene glycol residues, based on 100 moles of total glycol component residues.

[0019] Cyclohexanediethanol (e.g., 1,2-cyclohexanediethanol, 1,3-cyclohexanediethanol, or 1,4-cyclohexanediethanol) is a component that helps improve the transparency and impact resistance of the prepared polyester copolymer. Preferably, it includes 5 to 40 moles of cyclohexanediethanol residues based on 100 moles of total glycol component residues. More preferably, it includes 10 to 35 moles of cyclohexanediethanol residues based on 100 moles of total glycol component residues.

[0020] Preferably, in the diol component used for the copolymerization of the polyester copolymer of the present invention, the molar ratio of the diol to the dicarboxylic acid or its derivative is 1.0:1 to 2.5:1. Herein, "molar ratio" refers to the molar ratio of the components introduced during the copolymerization of the polyester copolymer. If the molar ratio is less than 1.0 or greater than 2.5, the color properties or transparency of the polyester copolymer may deteriorate. [Recycled diterephthalate] [(2-)] [Hydroxyethyl] [)] [ester]

[0021] As used herein, the term "recycled bis(2-hydroxyethyl) terephthalate" refers to material obtained from waste plastics collected after use. PET and PETG and their analogues are examples of waste plastics from which bis(2-hydroxyethyl) terephthalate can be obtained. For example, bis(2-hydroxyethyl) terephthalate can be obtained from PEG collected after use by saccharification, hydrolysis, methanololysis, etc., and such methods are widely known in the art.

[0022] Because recycled bis(2-hydroxyethyl) terephthalate undergoes numerous chemical steps during its acquisition from waste plastics, the quality of the product may inevitably deteriorate when it is used as a monomer in copolymers. In particular, when used as a monomer in polyester copolymers, color quality may deteriorate, and, as described later, a large amount of byproducts may be generated.

[0023] Therefore, this invention uses recycled bis(2-hydroxyethyl) terephthalate as the main monomer constituting the polyester copolymer of this invention, but controls the polyester copolymer to include 5 to 70% by weight of recycled bis(2-hydroxyethyl) terephthalate residues. If the content of recycled bis(2-hydroxyethyl) terephthalate is less than 5% by weight, the content of the aforementioned diol can be relatively increased. Therefore, byproducts derived from the diol component, especially byproducts derived from ethylene glycol, may increase, leading to a deterioration in the quality of the polyester copolymer. Furthermore, if the content of recycled bis(2-hydroxyethyl) terephthalate is greater than 70% by weight, the color properties and transparency of the polyester copolymer may deteriorate.

[0024] Preferably, the purity of the recovered bis(2-hydroxyethyl) terephthalate is 85% or higher. Since the recovered bis(2-hydroxyethyl) terephthalate is obtained from waste plastics collected after use, it may contain impurities. If the content of such impurities increases, these impurities may also be partially included in the prepared polyester copolymer, leading to deterioration of properties such as color and haze. In particular, if the purity of the recovered bis(2-hydroxyethyl) terephthalate is low, it may be difficult to achieve the required heat-shrinkable film shrinkage rate; therefore, it is preferable that the purity of the recovered bis(2-hydroxyethyl) terephthalate is high.

[0025] More preferably, the purity of the recovered bis(2-hydroxyethyl) terephthalate is 86% or higher, 87% or higher, 88% or higher, 89% or higher, 90% or higher, 91% or higher, 92% or higher, 93% or higher, 94% or higher, or 95% or higher. Theoretically, the upper limit of the purity of the recovered bis(2-hydroxyethyl) terephthalate is 100%, but for example, it may be 99% or lower, 98% or lower, or 97% or lower. The purity of the recovered bis(2-hydroxyethyl) terephthalate can be measured by liquid chromatography or similar methods, and the specific method for measuring purity will be specified in the examples described later. [Polyester copolymer]

[0026] The polyester copolymer of the present invention can be prepared by copolymerizing recycled bis(2-hydroxyethyl) terephthalate, dicarboxylic acid or its derivatives with ethylene glycol and the above-mentioned comonomers. The copolymerization may include sequentially performing an esterification reaction (step 1) and a condensation polymerization reaction (step 2).

[0027] The esterification reaction is carried out in the presence of an esterification catalyst, and esterification catalysts containing zinc compounds can be used. Specific examples of such zinc catalysts include zinc acetate, zinc acetate dihydrate, zinc chloride, zinc sulfate, zinc sulfide, zinc carbonate, zinc citrate, zinc gluconate, or mixtures thereof. Furthermore, the amounts of each starting material are as described above.

[0028] Esterification can be carried out at pressures of 0 to 10.0 kg / cm² and temperatures of 150 to 300°C. The esterification conditions can be appropriately controlled according to the specific properties of the polyester being prepared, the component ratios, or the process conditions. Specifically, preferred examples of esterification conditions may include pressures of 0 to 5.0 kg / cm², more preferably 0.1 to 3.0 kg / cm², and temperatures of 200 to 270°C, more preferably 240 to 260°C.

[0029] Furthermore, the esterification reaction can be carried out in batches or continuously, and the raw materials can be introduced separately, but preferably in slurry form, wherein the dicarboxylic acid component and the recovered bis(2-hydroxyethyl) terephthalate are mixed with the glycol component. Alternatively, the glycol component (e.g., isosorbide) which is solid at room temperature can be dissolved in water or ethylene glycol and then mixed with the dicarboxylic acid component (e.g., terephthalic acid) to form a slurry. Alternatively, isosorbide can be melted at a temperature of 60°C or above and then mixed with the dicarboxylic acid component (e.g., terephthalic acid) and other glycol components to form a slurry. Additionally, water can be added to the mixed slurry to help increase its fluidity.

[0030] The esterification product can be reacted for 1 to 24 hours at a temperature of 150 to 300°C and a reduced pressure of 600 to 0.01 mmHg to carry out condensation polymerization.

[0031] This condensation polymerization reaction can be carried out at a reaction temperature of 150 to 300 °C, preferably 200 to 290 °C, and more preferably 260 to 280 °C; and under reduced pressure of 600 to 0.01 mmHg, preferably 200 to 0.05 mmHg, and more preferably 100 to 0.1 mmHg. By applying reduced pressure to the condensation polymerization reaction, the byproduct ethylene glycol can be removed. Therefore, if the reduced pressure of the condensation polymerization reaction does not fall within 400 to 0.01 mmHg, the removal of the byproduct may be insufficient. Furthermore, when the condensation polymerization reaction is carried out outside the temperature range of 150 to 300°C, if the condensation polymerization reaction is carried out at or below 150°C, the byproduct ethylene glycol may not be effectively removed. Therefore, the intrinsic viscosity of the final reaction product may decrease, and the properties of the prepared resin may deteriorate. If the reaction is carried out at or above 300°C, the prepared polyester resin may turn yellow. In addition, the condensation polymerization reaction can proceed for a period of time until the intrinsic viscosity of the final reaction product reaches an appropriate level, for example, an average residence time of 1 to 24 hours.

[0032] In addition, condensation polymerization reactions can use condensation polymerization catalysts, which include titanium-based compounds, germanium-based compounds, antimony-based compounds, aluminum-based compounds, tin-based compounds, or mixtures thereof.

[0033] Examples of titanium-based compounds include tetraethyl titanate, tripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, octyl glycol titanate, lactate titanate, triethanolamine titanate, acetoacetone titanate, ethylacetate titanate, isostearate titanate, titanium dioxide, and the like. Examples of germanium-based compounds include germanium dioxide, germanium tetrachloride, germanium glycol, germanium acetate, copolymers thereof, mixtures thereof, and the like. Preferably, germanium dioxide can be used, and crystalline and amorphous germanium dioxide, as well as glycol-soluble germanium dioxide, can be used.

[0034] Meanwhile, the intrinsic viscosity of the polyester copolymer of the present invention is 0.50 to 1.0 dl / g, preferably 0.50 to 0.85 dl / g, and more preferably 0.55 to 0.80 dl / g. The method for measuring intrinsic viscosity will be specified in the examples described later.

[0035] Furthermore, preferably, the haze of the polyester copolymer of the present invention is 3 or less, more preferably 2.5 or less, 2.0 or less, 1.5 or less, or 1.0 or less. In addition, the lower limit of haze is theoretically 0, but in the present invention, it may 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 haze will be specified in the examples described later.

[0036] Furthermore, preferably, for a 6 mm polyester copolymer sample of the present invention, the "(Hunter L value) - (Hunter b value)" (hereinafter referred to as Plaque Color Lb) is 80 or above, more preferably, 81 or above, 82 or above, 83 or above, 84 or above, 85 or above, 86 or above, 87 or above, 88 or above, 89 or above, or 90 or above. Additionally, the upper limit of Plaque Color Lb can be 100, and in the present invention, it can be 99 or below, 98 or below, 97 or below, 96 or below, or 95 or below. The method for measuring Plaque Color Lb will be specified in the examples described later.

[0037] According to the present invention, an article comprising a polyester copolymer is also provided.

[0038] The polyester copolymer prepared by the above method can be in the form of fragments, lumps, or powder before molding, or it can be in the form of a molded article formed by various molding processes (e.g., extrusion or injection), such as a film, heat-shrinkable film, or sheet. Another type of molded product according to the invention may contain the above-mentioned polyester copolymer, and the molded product may be a heat-shrinkable film. This heat-shrinkable film exhibits a maximum heat shrinkage rate of 45% or less at 70°C and a maximum heat shrinkage rate of 70% or more at 95°C. Therefore, it contains recycled monomers but exhibits heat shrinkage properties equivalent to those of films previously known to be obtained from polyester resins and the like. The methods for measuring the shrinkage rate at 70°C and 95°C will be specified in the examples described later. [Beneficial Effects]

[0039] The polyester copolymers of the present invention described above can be extruded and molded, and therefore can be used to prepare various containers. Implementation

[0040] In the following sections, preferred embodiments will be presented to better understand the invention. However, these embodiments are presented only for the purpose of better understanding the invention, and the scope of the invention is not limited thereto. [example] [1]

[0041] Recovered bis(2-hydroxyethyl) terephthalate (1485.3 g; hereinafter referred to as "r-BHET"), TPA (terephthalic acid; 2034.6 g), EG (ethylene glycol; 367.0 g), CHDM (1,4-cyclohexanediethanol; 826.4 g), and DEG (diethylene glycol; 211.1 g) with a purity of 93% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. TiO2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, Polysynthren Blue RLS (Clarient Inc., 0.006 g) as a blue colorant, and Solvaperm Red BB (Clarient Inc., 0.004 g) as a red colorant.

[0042] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 255°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 255°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0043] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 285°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [example] [2]

[0044] r-BHET (2298.7 g), TPA (1119.5 g), EG (6.9 g), CHDM (721.0 g), and DEG (217.6 g) with a purity of 98% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. TiO2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, and cobalt acetate (0.7 g) as a colorant.

[0045] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 255°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 255°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0046] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 285°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [example] [3]

[0047] r-BHET (403.0 g), TPA (2370.1 g), EG (550.8 g), CHDM (685.3 g), and DEG (235.4 g) with a purity of 90% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. TiO2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, and cobalt acetate (0.7 g) as a colorant.

[0048] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 255°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 255°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0049] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 285°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [example] [4]

[0050] r-BHET (4128.2 g), TPA (674.5 g), CHDM (877.7 g), and DEG (387.6 g) with a purity of 85% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. TiO2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, and cobalt acetate (1.0 g) as a colorant.

[0051] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 255°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 255°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0052] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 285°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [example] [5]

[0053] r-BHET (2515.0 g), TPA (1224.8 g), EG (79.3 g), CHDM (522.5 g), and DEG (311.4 g) with a purity of 99% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. TiO2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, Polysynthren Blue RLS (Clarient Inc., 0.007 g) as a blue colorant, and Solvaperm Red BB (Clarient Inc., 0.004 g) as a red colorant.

[0054] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 255°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 255°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0055] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 285°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [example] [6]

[0056] r-BHET (1424.4 g), TPA (2279.2 g), EG (695.4 g), CHDM (222.8 g), DEG (282.3 g), and a CHDM derivative (311.0 g; containing i) 4-(hydroxymethyl)cyclohexanecarboxylic acid (4-(hydroxymethyl)cyclohexylmethyl) ester and ii) 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol in a molar ratio of 1:3) were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. GeO₂ (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, Polysynthren Blue RLS (Clarient Inc., 0.013 g) as a blue colorant, and Solvaperm Red BB (Clarient Inc., 0.004 g) as a red colorant.

[0057] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 1.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 1495.6 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 265°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 265°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0058] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 275°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.65 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [example] [7]

[0059] r-BHET (3695.6 g), TPA (603.8 g), EG (157.9 g), CHDM (261.9 g), DEG (239.0 g), and a CHDM derivative (341.2 g; containing i) 4-(hydroxymethyl)cyclohexanecarboxylic acid (4-(hydroxymethyl)cyclohexylmethyl) ester and ii) 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol in a molar ratio of 6:1) were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. GeO₂ (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, Polysynthren Blue RLS (Clarient Inc., 0.020 g) as a blue colorant, and Solvaperm Red BB (Clarient In.c., 0.008 g) as a red colorant.

[0060] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 0.5 kgf / cm² higher than atmospheric pressure (absolute pressure: 1127.8 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 260°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 260°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0061] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 275°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature, and the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.80 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor and twisted, then solidified with a coolant, and subsequently granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [example] [8]

[0062] r-BHET (603.6 g), DMT (dimethyl terephthalate; 2612.2 g), EG (1070.6 g), CHDM (707.2 g), and DEG (231.3 g) with a purity of 86% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. Manganese(II) acetate tetrahydrate (1.5 g) and Sb₂O₃ (1.8 g) were introduced as catalysts, and cobalt acetate (0.6 g) was introduced as a colorant.

[0063] Nitrogen gas was then introduced into the reactor, bringing the reactor pressure to atmospheric pressure. The reactor temperature was then raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 240°C over the next 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 240°C for esterification. During this process, byproducts were discharged through a tubing and condenser. After esterification was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0064] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 265°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in the viscosity of the reactants, or the temperature of the reactants rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [example] [9]

[0065] r-BHET (1245.6 g), TPA (1899.4 g), IPA (isophthalic acid; 814.0 g), EG (560.4 g), CHDM (746.2 g), and DEG (310.2 g) with a purity of 87% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. GeO2 (1.0 g) was introduced as a catalyst, and cobalt acetate (0.6 g) was introduced as a colorant.

[0066] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 255°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 255°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0067] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 285°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [Comparative Example] [1]

[0068] r-BHET (4368.6 g), TPA (150.3 g), EG (78.6 g), CHDM (834.3 g), and DEG (211.1 g) with a purity of 81% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. TiO2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, and cobalt acetate (0.8 g) as a colorant.

[0069] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 255°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 255°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0070] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 285°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [Comparative Example] [2]

[0071] r-BHET (3732.6 g), TPA (183.6 g), CHDM (694.0 g), and DEG (226.1 g) with a purity of 90% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. TiO2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, and cobalt acetate (0.7 g) as a colorant.

[0072] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 255°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 255°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0073] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 285°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [Comparative Example] [3]

[0074] r-BHET (1424.4 g), TPA (2279.2 g), EG (1798.4 g), CHDM (139.2 g), DEG (705.8 g), and CHDM derivative (414.6 g; containing i) 4-(hydroxymethyl)cyclohexanecarboxylic acid (4-(hydroxymethyl)cyclohexylmethyl) ester and ii) 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol in a molar ratio of 5:1, were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. GeO 2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, Polysynthren Blue RLS (Clarient Inc., 0.013 g) as a blue toner, and Solvaperm Red BB (Clarient Inc., 0.004 g) as a red toner.

[0075] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 1.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 1495.6 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 265°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 265°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0076] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 275°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in reactant viscosity or the reactant temperature rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.65 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor, twisted, and solidified with a coolant, then granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [Comparative Example] [4]

[0077] r-BHET (2415.8 g), TPA (1578.8 g), EG (117.9 g), and CHDM (821.7 g) with a purity of 86% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. GeO₂ (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, and cobalt acetate (0.7 g) as a colorant.

[0078] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 265°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 265°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0079] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 270°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in the viscosity of the reactants, or the temperature of the reactants rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.60 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor and twisted, then solidified with a coolant, and subsequently granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [Comparative Example] [5]

[0080] r-BHET (1788.7 g), TPA (1169.0 g), EG (174.6 g), and DEG (411.3 g) with a purity of 85% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. GeO₂ (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, and cobalt acetate (0.1 g) as a colorant.

[0081] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 265°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 265°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0082] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 280°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in the viscosity of the reactants, or the temperature of the reactants rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor and twisted, then solidified with a coolant, and subsequently granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer. [Comparative Example] [6]

[0083] r-BHET (2257.0 g), TPA (1475.4 g), EG (121.2 g), CHDM (742.3 g), and DEG (519.1 g) with a purity of 83% were introduced into a 10 L reactor, which was connected to a tubular column and a water-cooled condenser. TiO2 (1.0 g) was introduced as a catalyst, phosphoric acid (1.5 g) as a stabilizer, and cobalt acetate (0.5 g) as a colorant.

[0084] Nitrogen gas was then introduced into the reactor to create a pressurized environment, with the reactor pressure 2.0 kgf / cm² higher than atmospheric pressure (absolute pressure: 2231.1 mmHg). Furthermore, the reactor temperature was raised to 220°C within 90 minutes and maintained at 220°C for 2 hours, followed by a further increase to 270°C over 2 hours. The mixture in the reactor was then visually observed until it became transparent, while the reactor temperature was maintained at 270°C to carry out the esterification reaction. During this process, byproducts were discharged through a tubing and condenser. After the esterification reaction was complete, the nitrogen gas inside the pressurized reactor was vented to reduce the reactor pressure to atmospheric pressure. The mixture was then transferred to a 7 L reactor for vacuum reaction.

[0085] Furthermore, the reactor pressure is reduced from atmospheric pressure to 5 Torr (absolute pressure: 5 mmHg) within 30 minutes, while the reactor temperature rises to 280°C within 1 hour, and the polymerization condensation reaction is carried out while the reactor pressure is maintained at or below 1 Torr (absolute pressure: 1 mmHg). At the start of the condensation polymerization reaction, the stirring speed is set to high, but as the polymerization condensation reaction proceeds, the stirring force decreases due to the increase in the viscosity of the reactants, or the temperature of the reactants rises above the predetermined temperature; the stirring speed can be appropriately controlled. The polymerization condensation reaction continues until the intrinsic viscosity (IV) of the mixture (molten material) in the reactor becomes 0.70 dl / g. If the intrinsic viscosity of the mixture in the reactor reaches the desired level, the mixture is discharged from the reactor and twisted, then solidified with a coolant, and subsequently granulated to achieve an average weight of approximately 12 to 14 mg, thereby producing a polyester copolymer.

[0086] In the exemplary and comparative examples, the content of the components introduced for preparing the polyester copolymer is shown in Table 1 below. Table 1 r-BHET Purity of r-BHET TPA IPA DMT EG CHDM DEG CHDM derivatives (diol) / (acid or derivative)1) unit Mo Er % Mo Er Mo Er Mo Er Mo Er Mo Er Mo Er Mo Er - Example 1 5.85 93 12.26 0 0 5.92 5.74 1.99 0 1.11 Example 2 9.05 98 6.74 0 0 0.11 5.01 2.05 0 1.06 Example 3 1.59 90 14.28 0 0 8.88 4.76 2.22 0 1.11 Example 4 16.25 85 4.06 0 0 0 6.09 3.66 0 2.40 Example 5 9.90 99 7.38 0 0 1.28 3.63 2.94 0 1.06 Example 6 5.61 98 13.73 0 0 11.22 1.55 1.93 1.16 1.15 Example 7 14.55 90 3.64 0 0 2.55 1.82 1.64 1.27 2.00 Example 8 2.38 86 0 0 13.19 17.27 4.91 1.58 0 1.76 Example 9 4.90 87 11.44 4.90 0 9.04 5.18 2.12 0 1.00 Comparative Example 1 17.20 81 0.91 0 0 1.27 5.79 1.99 0 10.00 Comparative Example 2 14.70 90 1.11 0 0 0 4.82 2.13 0 6.29 Comparative Example 3 5.61 91 13.73 0 0 29.01 0.97 4.83 1.55 2.65 Comparative Example 4 9.51 86 9.51 0 0 1.90 5.71 0.00 0 0.80 Comparative Example 5 7.04 85 7.04 0 0 2.82 0 2.82 0 0.80 Comparative Example 6 8.89 83 8.89 0 0 1.96 5.16 3.56 0 1.20 1) (Diol) / (Acid or Derivative) = (EG + CHDM + DEG + CHDM Derivative) / (TPA + IPA + DMT) [Experimental Example]

[0087] The properties of the copolymers prepared in the exemplary and comparative examples are evaluated as follows. 1) Purity of r-BHET

[0088] The purity of r-BHET was measured by diluting 0.01 g of the sample in 20 ml of methanol or chloroform using liquid chromatography. The purity (area %) in total BHET was confirmed by integrating the peak areas of the measured spectra. 2) Residue composition

[0089] After the sample was dissolved in CDCl3 solvent at a concentration of 3 mg / mL, 1H-NMR spectra were obtained at 25 °C using a nuclear magnetic resonance apparatus (JEOL, 600 MHz FT-NMR) to confirm the composition (moles %) of diols derived from the polyester resin and the composition (weight %) of r-BHET derived from it. The composition of residues derived from diols was analyzed as the moles of residues derived from each specific diol (DEG and CHDM) relative to the total composition of all residues derived from the diol. 3) Intrinsic viscosity

[0090] After dissolving the polyester copolymer in o-chlorophenol (OCP) at a concentration of 0.12% at 150°C, the intrinsic viscosity was measured using an Ubbelohde viscometer in a thermostat at 35°C. Specifically, the temperature of the tube viscometer was maintained at 35°C, and the time t0 (outflow time) required for the solvent to pass through a specific internal region of the tube viscometer and the time t0 required for the solution to pass through between them were calculated. Subsequently, the values ​​of t0 and tt were substituted into Equation 1 to calculate the specific viscosity, and the specific viscosity value was substituted into Equation 2 to calculate the intrinsic viscosity. Equation 1 Equation 2 4) Plaque color Lb

[0091] The color and luminance of the samples were measured using a Varian Cary 5 UV / Vis / NIR spectrophotometer equipped with a diffuse reflectance element. Six-millimeter-thick polyester resin samples were prepared, and transmission data were obtained using an Illuminant D65 at a 2° observation angle. The data were processed using a color analyzer in Grams / 32 software to calculate the Hunter L*a*b* values, with Lb described in the table below. 5) Haze

[0092] Prepare 6 mm thick polyester resin samples and measure the haze of the samples using a CM-3600A measuring instrument (Minolta Inc.) according to ASTM D1003-97 method. 6) Shrinkage rate

[0093] Polyester resins prepared in the examples and comparative examples were extruded through a mold at a temperature of 250°C to 290°C, and then cooled to 20°C to 50°C to obtain an unstretched film. Subsequently, the unstretched film was reheated to 75°C to 95°C, causing it to stretch 5 times laterally to form a polyester film. The thickness of the prepared polyester film was 45 micrometers.

[0094] The prepared polyester film was cut into 5 cm x 5 cm square pieces and stretched at a stretching ratio (DR) of MD:TD=1:5 and a stretching temperature of 75 to 95°C while being reheated. Then, it was placed in a hot water bath at the temperature described in Table 1 below for 30 seconds to shrink. The vertical length and horizontal length of the sample were then measured, and the shrinkage rate was calculated according to the following equation. - Heat shrinkage rate (%) = 100 × (length before shrinkage – length after shrinkage) / (length before shrinkage)

[0095] The results are shown in Table 2 below. Table 2 r-BHET DEG CHDM (Diol) / (Acid or Derivative) intrinsic viscosity Plaque Color Lb Haze Shrinkage rate at 70℃ Shrinkage rate at 95℃ unit weight% Moer% Moer% - dg / l - - - - Example 1 29.6 8.0 31.0 1.11 0.70 88 1 38.2% 70.0% Example 2 49.0 9.5 31.0 1.06 0.70 87 1 45.0% 78.0% Example 3 10.0 11.0 29.0 1.11 0.70 90 1 38.2% 78.0% Example 4 61.8 13.0 29.0 2.40 0.70 87 1 45.0% 77.0% Example 5 51.6 13.0 20.0 1.06 0.70 85 1 44.0% 72.0% Example 6 29.5 11.5 14.5 1.15 0.65 85 1.5 32.7% 70.0% Example 7 70.1 11.5 14.5 2.00 0.80 82 0.8 27.2% 75.0% Example 8 12.7 8.0 31.0 1.50 0.70 85 3 32.7% 75.0% Paradigm 9 41.0 13.0 20.0 1.00 0.70 85 3 45.0% 72.0% Comparative Example 1 71.7 8.0 31.0 10.00 0.70 80 4 46.0% 75.0% Comparative Example 2 70.6 13.0 29.0 6.29 0.70 80 4 58.8% 75.0% Comparative Example 3 23.8 11.5 14.5 2.65 0.65 80 1.5 52.0% 65.0% Comparative Example 4 47.2 0.0 30.0 0.80 0.60 75 10 9.4% 55.0% Comparative Example 5 51.6 25.0 0.0 0.80 0.70 70 1.5 65.0% 75.0% Comparative Example 6 43.5 11 29 1.2 0.70 70 4 50.0% 75.0%

[0096] As shown in Table 2, Examples 1 to 9 of the present invention exhibit excellent results in terms of color properties, haze, and shrinkage. Conversely, in Comparative Examples 1 and 2, the color properties and haze deteriorated due to the high content of the portion derived from recycled r-BHET. Furthermore, in Comparative Example 2, although the content of the portion derived from r-BHET was within 70% by weight, the color properties deteriorated because the diol value / acid value was greater than 2.5.

[0097] Furthermore, since the glycol value / acid value of the heat shrink film prepared using the resins of Comparative Examples 1 to 3 is greater than 2.5, byproducts and side reactions increase due to the introduction of a large amount of glycol. Therefore, the shrinkage rate at 70°C is greater than 45%, and due to excessive shrinkage at temperature, it cannot be used in commercial heat shrink film manufacturing processes. In addition, in the cases of Comparative Examples 4 and 5, since DEG and CHDM were not used respectively, the color properties and haze deteriorated. In addition, in the case of Comparative Example 6, since the purity of r-BHET is low and the impurity content exceeds a certain level, the low-temperature (70°C) shrinkage rate of the final product increases due to impurities, making it difficult to apply to commercial processes.

[0098] Therefore, it can be confirmed that in this invention, when the content of the portion derived from r-BHET is 70% by weight or less and the diol value / acid value is 2.5 or less, excellent effects can be exhibited in terms of color properties, haze and shrinkage.

Claims

1. A polyester copolymer polymerized from the following: 1) recycled bis(2-hydroxyethyl) terephthalate, 2) an acid comprising a dicarboxylic acid or a derivative thereof, and 3) a diol comprising diethylene glycol and a comonomer, having a structure in which the portions derived from the bis(2-hydroxyethyl) terephthalate, the portions derived from the dicarboxylic acid or a derivative thereof, and the portions derived from the diol are repeated, wherein the recycled bis(2-hydroxyethyl) terephthalate has a purity of 85% or more, and wherein the polyester copolymer includes a portion derived from the recycled bis(2-hydroxyethyl) terephthalate in an amount of 5 to 70% by weight, the diethylene glycol residues are included in an amount of 5 to 50 moles, based on 100 moles of total diol component residues, and the mole ratio of the diol to the dicarboxylic acid or a derivative thereof is 1.0:1 to 2.5:

1.

2. The polyester copolymer of claim 1, wherein the comonomer is ethylene glycol, cyclohexanediol, cyclohexanediol derivatives or combinations thereof.

3. The polyester copolymer of claim 2, wherein the cyclohexanediethanol derivative is 4-(hydroxymethyl)cyclohexanecarboxylic acid (4-(hydroxymethyl)cyclohexylmethyl) ester or 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylethanol.

4. The polyester copolymer of claim 3, wherein the polyester copolymer comprises 0.1 to 25 moles of a diol portion derived from 4-(hydroxymethyl)cyclohexanecarboxylic acid (4-(hydroxymethyl)cyclohexylmethyl) ester and 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol, based on the total diol portion.

5. The polyester copolymer of claim 1, wherein the comonomer further comprises 1,2-propanediol, 1,3-propanediol, 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, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, or mixtures thereof.

6. The polyester copolymer of claim 1, wherein the acid comprising dicarboxylic acid or a derivative thereof comprises terephthalic acid.

7. The polyester copolymer of claim 6, wherein the acid comprising a dicarboxylic acid or a derivative thereof comprises one or more acids selected from the group consisting of isophthalic acid, dimethyl isophthalate, phthalic acid, dimethyl phthalate, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, dimethyl 2,6-naphthalenedicarboxylic acid, diphenyl dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, dimethyl 1,4-cyclohexanedicarboxylic acid, dimethyl 1,3-cyclohexanedicarboxylic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, glutaric acid, and azelaic acid.

8. The polyester copolymer of claim 1, wherein the intrinsic viscosity of the polyester copolymer is 0.50 to 1.0 dl / g.

9. The polyester copolymer of claim 1, wherein the haze of the polyester copolymer is 3 or less.

10. The polyester copolymer of claim 1, wherein a 6 mm thick sample of the polyester copolymer has a (Hunter L value) - (Hunter b value) of 80 or above.

11. An article comprising a polyester copolymer as claimed in any one of claims 1 to 10.

12. The article of claim 11, wherein the article is a film.

13. The product of claim 12, wherein the shrinkage rate of the film at 70°C is 45% or less.

14. The product of claim 12, wherein the film has a shrinkage rate of 70% or more at 95°C.