Polyester resins, methods for making same, and articles produced therefrom

Abstract

The present invention relates to a polyester resin, a method for producing the same, and articles produced therefrom. Specifically, the method for producing the polyester resin includes the steps of: (1) preparing a reactant mixture containing a first glycol component and an acid component; (2) subjecting the reactant mixture to a first esterification reaction to obtain a first reactant; and (3) subjecting the first reactant to a second esterification reaction to obtain a second reactant. The present invention significantly reduces by-products produced during the method for producing the polyester resin.

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to a method for preparing a polyester resin, in which the process residence time of the glycol component in the preparation of the polyester resin is controlled, to the polyester resin prepared by the method, and to articles comprising the polyester resin.

[0002] [Background technology] Among polymers, polyesters are used as materials in various fields due to their excellent mechanical strength, heat resistance, transparency, and gas barrier properties. In particular, polyester films or plates prepared using polyester resins have good transparency and excellent mechanical strength, and are therefore widely used in cases, boxes, partitions, shelves, panels, packaging materials, building materials, interior and exterior materials, etc.

[0003] Such polyester resins can be prepared by a continuous process in which an acid component and a glycol component are directly esterified and / or transesterified in the presence of a polymerization catalyst, followed by polycondensation. To ensure smooth operation of this continuous process, the fluidity of the slurry in which the acid component and the glycol component are mixed and the reactivity of each reaction process must be ensured. For this reason, the glycol component is generally added in excess in the initial charging step.

[0004] However, an excessive amount of glycol component generates by-products due to the influence of heat during each reaction process, which acts as a factor in reducing the quality of the polyester resin. In addition, an excessive amount of glycol component used causes problems in terms of increasing the production cost of the polyester resin.

[0005] [Prior art document] [Patent documents] (Patent Document 1) Korean Patent Application Publication No. 2014-0071536

[0006] [DISCLOSURE OF THE INVENTION] [Technical issues] The present inventors have conducted various studies to solve the above-mentioned problems that have existed until now, and as a result, have found that when the residence time of the glycol component in the process is shortened in the preparation of a polyester resin by a continuous process, the generation of side reaction products resulting from the thermal decomposition of the glycol component is minimized, thereby enabling the preparation of a high-quality polyester resin.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a high quality polyester resin and a method for preparing the same.

[0008] Additionally, another object of the present invention is to provide an article comprising the polyester resin.

[0009] [Methods for solving the problem] In order to achieve the above object, the present invention provides a method for preparing a polyester resin, comprising the steps of: (1) preparing a reaction raw material containing a first glycol component and an acid component; (2) subjecting the reaction raw material to a first esterification reaction to obtain a first reactant; and (3) subjecting the first reactant to a second esterification reaction to obtain a second reactant, wherein at least one second glycol component having a carbon number of 2 or more is added in portions throughout steps (1) to (3), or in portions throughout steps (2) and (3), or all at once in step (3).

[0010] Additionally, the present invention provides a polyester resin prepared by the above method.

[0011] Additionally, the present invention provides an article comprising the polyester resin.

[0012] [Advantageous effects of the invention] In the continuous process for preparing the polyester resin of the present invention, the glycol component (second glycol component) is added in portions to each reaction process (step) or all at once to a later reaction process (step) to prepare the polyester resin; thus, the process residence time of the glycol component is shortened, thereby minimizing the conversion of the glycol component to side reactants due to the influence of heat in each reaction process.

[0013] Therefore, the present invention can provide a polyester resin of high quality (excellent color, moldability, etc.) and, since an article is prepared using such a polyester resin, it is possible to provide an article (e.g., a polyester film) with excellent physical properties.

[0014] Meanwhile, in the present invention, glycol by-products (e.g., by-reaction products, unreacted glycol components, etc.) formed in each reaction process (step) are recovered and purified to obtain purified products, which can be reused as reaction raw materials; thus, polyester resins can be prepared in an economical manner. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a flow chart illustrating a method for preparing a polyester resin according to an embodiment of the present invention.

[0016] [Best Mode for Carrying Out the Invention] The present invention will be described in detail below. The present invention is not limited to the following disclosure, and can be modified in various forms as long as the gist of the invention is not changed.

[0017] As used herein, the term "comprising" is intended to specify certain features, regions, steps, processes, elements, and / or components and does not exclude the presence or addition of other features, regions, steps, processes, elements, and / or components, unless specifically stated to the contrary.

[0018] Throughout this specification, the terms first, second, etc. are used to describe various components. However, these components should not be limited by such terms. These terms are used only to distinguish one element from another.

[0019] All numbers and expressions used herein regarding quantities of ingredients, reaction conditions, and the like, should be understood to be modified by the term "about" unless otherwise indicated.

[0020] (Method for preparing polyester resin) The present invention provides a method for preparing a polyester resin in which the injection point of a glycol component is controlled to shorten the process residence time of the glycol component. Specifically, the method for preparing a polyester resin according to the present invention includes the steps of: (1) preparing a reactant containing a first glycol component and an acid component; (2) subjecting the reactant to a first esterification reaction to obtain a first reactant; and (3) subjecting the first reactant to a second esterification reaction to obtain a second reactant, wherein at least one second glycol component having a carbon number of 2 or more is added in portions throughout steps (1) to (3), or in portions throughout steps (2) and (3), or all at once in step (3).

[0021] The method for preparing a polyester resin according to the present invention optionally further comprises each of the steps of (4) subjecting the second reactant to polycondensation to obtain a third reactant comprising a polymer, and (5) recovering and purifying the glycol by-product formed in any one or more of steps (2) through (4).

[0022] Hereinafter, the method for preparing the polyester resin according to the present invention will be described in detail as follows in conjunction with FIG.

[0023] Step (1): Preparation of reaction materials According to the present invention, step (1) is a step of preparing a reaction feedstock containing a first glycol component and an acid component. Specifically, step (1) may include charging the first glycol component and the acid component into a predetermined container and mixing them to prepare a reaction feedstock slurry, or charging the first glycol component and the acid component into a continuous reactor in which a first esterification reaction is carried out and mixing them.

[0024] The first glycol component is not particularly limited as long as it is a compound having two or more carbon atoms (particularly, 2 to 10 carbon atoms) and two hydroxy groups (OH). Specifically, the first glycol component may be ethylene glycol, recycled ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, recycled 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, recycled 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, bis-2-hydroxyethyl terephthalate, recycled bis-2-hydroxyethyl terephthalate, The first glycol component may include at least one selected from the group consisting of methyl methyl 4-(hydroxymethyl)cyclohexanecarboxylate, isosorbide, regenerated isosorbide, cyclohexanedimethanol derivatives (e.g., 4-(hydroxymethyl)cyclohexylmethyl 4-(hydroxymethyl)cyclohexanecarboxylate; 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol, etc.), 2,2,4,4-tetramethyl-1,3-cyclobutanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymers of ethylene oxide and tetrahydrofuran, ethylene oxide-added polypropylene glycol, polycarbonate diol, polyneopentyl glycol, poly-3-methylpentanediol, and poly-1,5-pentanediol. Preferably, the first glycol component may include ethylene glycol, which is economical and can increase the fluidity of the reaction raw material slurry.

[0025] The acid component is not particularly limited as long as it is a compound having two carboxyl groups (COOH). Specifically, the acid component may include at least one selected from the group consisting of terephthalic acid, recycled terephthalic acid, isophthalic acid, dimethyl terephthalate, recycled dimethyl terephthalate, adipic acid, sebacic acid, succinic acid, isodecyl succinic acid, maleic acid, fumaric acid, glutaric acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 4,4'-stilbenedicarboxylic acid, 2,5-furandicarboxylic acid, and 2,5-thiophenedicarboxylic acid. Preferably, the acid component may include at least one selected from the group consisting of terephthalic acid and isophthalic acid.

[0026] The reaction feed comprising the first glycol component and the acid component may not include the second glycol component, or may include a second glycol component added in portions, a detailed description of which is provided below.

[0027] On the other hand, in preparing the reaction raw material slurry, an additive including at least one selected from the group consisting of a catalyst, a stabilizer, a colorant, a crystallization agent, an antioxidant, and a branching agent may be further used as a raw material in addition to the reaction raw materials.

[0028] The catalyst may be sodium and magnesium methylates; acetates, borates, fatty acid salts, or carbonates of Zn, Cd, Mn, Co, Ca, and Ba; or oxides of Mg, Pb, Mn, Ti, Zn, Si, Sb, and Ge, or hydrates thereof. For example, the catalyst may be tetraethyl titanate, acetyltripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, octylene glycol titanate, triethanolamine titanate, acetylacetonate titanate, ethyl acetoacetate titanate, isostearyl titanate, titanium dioxide, germanium dioxide, germanium tetrachloride, germanium ethyleneglycoxide, germanium acetate, or a combination thereof.

[0029] As stabilizers, phosphorus compounds such as phosphoric acid, trimethyl phosphate, and triethyl phosphate can be used.

[0030] As colorants, organic compounds such as cobalt-based compounds, anthraquinone-based compounds, perinone-based compounds, azo-based compounds, and methine-based compounds (e.g., cobalt acetate, cobalt propionate, Clariant's Polysynthren Blue RLS toner, and Clariant's Solvaperm Red BB toner) can be used.

[0031] As the crystallizing agent, a crystal nucleating agent, an ultraviolet absorber, a polyolefin resin, a polyamide resin, etc. can be used.

[0032] As the antioxidant, hindered phenol compounds, phosphite compounds, thioether compounds, etc. can be used.

[0033] As the branching agent, trimellitic anhydride, trimethylolpropane, trimellitic acid, etc. can be used.

[0034] Step (2): First esterification reaction According to the present invention, step (2) is a step of subjecting the reactant to a first esterification reaction to obtain a first reactant. In particular, step (2) may include a procedure of subjecting continuously supplied reactant to a first esterification reaction in a continuous reactor (first continuous reactor) to produce a first reactant containing an oligomer (first oligomer).

[0035] The conditions under which the first esterification reaction is carried out are not particularly limited. Specifically, the temperature at which the first esterification reaction is carried out may be 120 to 280°C, 140 to 280°C, 160 to 280°C, 180 to 278°C, 200 to 275°C, or 220 to 260°C. The pressure at which the first esterification reaction is carried out is 0.1 to 5 kgf / cm. 2 , 0.2~4.5kgf / cm 2 , 0.3~4kgf / cm 2, 0.4~3.5kgf / cm 2 , or 0.5 to 3 kgf / cm 2 The time for which the first esterification reaction is carried out may be 0.5 to 5 hours, 0.5 to 4 hours, 1 to 3.5 hours, or 1.5 to 3 hours. When the first esterification reaction is carried out under the above conditions, the production of side products (e.g., diethylene glycol esters, etc.) is minimized while the desired oligomer can be obtained in high yield.

[0036] The molecular weight (Mn) of the oligomer contained in the first reactant is not particularly limited, but may be, for example, 855 to 3,000 g / mol, 870 to 2,600 g / mol, 885 to 2,000 g / mol, 900 to 1,600 g / mol, or 900 to 1,200 g / mol. When the molecular weight of the oligomer contained in the first reactant is within the above range, a high-quality polyester resin can be prepared in high yield.

[0037] The second glycol component, which is one of the reactants, is not provided in the first esterification reaction; instead, the second glycol component may be provided in separate increments, a detailed description of which is provided below.

[0038] According to the present invention, the first esterification reaction can be carried out with a molar ratio (G / A) of the glycol component to the acid component controlled within a specific range. Specifically, in the first esterification reaction, the G / A value according to the following formula 2 can be 1.2 or less, 1.18 or less, 1.16 or less, 1.14 or less, 1.12 or less, or 1.1 or less. More specifically, the G / A value can be 0.88 to 1.2, 0.88 to 1.19, 0.89 to 1.18, 0.89 to 1.17, 0.90 to 1.16, 0.90 to 1.15, 0.91 to 1.14, 0.91 to 1.13, 0.92 to 1.12, or 0.92 to 1.1. When the G / A value is within the above range, the reactivity of the glycol components (the first glycol component and the second glycol component) is ensured in the second esterification reaction, thereby significantly reducing the occurrence of side reactions caused by heat. [Formula 2] G / A = (molar ratio of first glycol component + mole ratio of second glycol component) / molar ratio of acid component

[0039] Meanwhile, by-products such as side reactants or unreacted glycol components formed in step (2) can be discharged (removed) from the continuous reactor and not subjected to step (5) described later. The side reactants can be, in particular, monohydroxyethyl terephthalate (MHET), bis-2-hydroxyethyl terephthalate (BHET), bis-2-hydroxyethyl terephthalate dimer (BHET dimer), diethylene glycol ester (DEG ester), or cyclic compounds, and the unreacted glycol components can be the first glycol component (e.g., ethylene glycol). Discharging the side reactants or unreacted glycol components from the continuous reactor can reduce the production of side reactants and control the G / A value in the first esterification reaction. Meanwhile, the by-products may also include unreacted acid components (e.g., terephthalic acid).

[0040] Step (3): Second esterification reaction According to the present invention, step (3) is a step of subjecting the first reactant to a second esterification reaction to obtain a second reactant. In particular, step (3) may include a procedure of subjecting the first reactant to a second esterification reaction (transesterification) in a continuous reactor (second continuous reactor) to produce a second reactant containing an oligomer (second oligomer).

[0041] The conditions under which the second esterification reaction is carried out are not particularly limited. In particular, the temperature under which the second esterification reaction is carried out may be 150 to 280°C, 180 to 280°C, 210 to 275°C, 230 to 275°C, 240 to 270°C, or 250 to 265°C. The pressure under which the second esterification reaction is carried out may be 0.1 to 5 kgf / cm. 2 , 0.2~4.5kgf / cm 2 , 0.3~4kgf / cm 2 , 0.4~3.5kgf / cm 2 , or 0.5 to 3 kgf / cm 2The time for which the second esterification reaction is carried out may be 2 to 9 hours, 3 to 8.5 hours, 3.5 to 8 hours, or 4 to 7.5 hours. When the second esterification reaction is carried out under the above conditions, the production of side products is minimized while the desired oligomer can be obtained in high yield.

[0042] The molecular weight (Mn) of the oligomer contained in the second reactant is not particularly limited, but may be 880 to 2,000 g / mol, 900 to 1,600 g / mol, 920 to 1,400 g / mol, 930 to 1,300 g / mol, or 940 to 1,250 g / mol. When the molecular weight of the oligomer contained in the second reactant is within the above range, a high-quality polyester resin can be prepared in high yield.

[0043] According to the present invention, the molecular weight change rate between the first reactant obtained by the first esterification reaction and the second reactant obtained by the second esterification reaction can be 90% or more. In particular, in the present invention, the molecular weight change rate (M RC ) can be 90% or more, 91% or more, 95% or more, 100% or more, 110% or more, 140% or more, 180% or more, 200% or more, or 220% or more. More specifically, the rate of change in molecular weight (M RC The rate of change in molecular weight (M) can be 90 to 230%, 90 to 220%, 91 to 190%, 100 to 170%, 100 to 160%, or 102 to 150%. RC ) is 90% or more means that each esterification reaction is carried out efficiently so that an oligomer having a molecular weight similar to or equivalent to that of the oligomer contained in the first reactant is produced in the second esterification reaction. As a result, the present invention can provide a polyester resin with excellent quality. [Formula 1] M RC =(Mn1 / Mn2)×100 where Mn1 is the number average molecular weight of the oligomers in the first reactant and Mn2 is the number average molecular weight of the oligomers in the second reactant.

[0044] Meanwhile, by-products such as side reactants or unreacted glycol components formed in the procedure of step (3) can be discharged (removed) from the continuous reactor and are not subjected to the procedure of step (5) described later. The side reactants can be, in particular, monohydroxyethyl terephthalate (MHET), bis-2-hydroxyethyl terephthalate (BHET), bis-2-hydroxyethyl terephthalate dimer (BHET dimer), diethylene glycol ester (DEG ester), or cyclic compounds, and the unreacted glycol components can be the first glycol component (e.g., ethylene glycol). Meanwhile, the by-products can further include unreacted acid components (e.g., terephthalic acid).

[0045] According to the present invention, the second glycol component, whether added in portions or all at once, can be fed to the second esterification reaction. That is, the first reactant and the second glycol component obtained in step (2) can be continuously fed to a continuous reactor in which the second esterification reaction is carried out. They can react to carry out a transesterification reaction in step (3).

[0046] Specifically, according to the present invention, at least one second glycol component having a carbon number of 2 or greater can be added in portions throughout steps (1) to (3), or in portions throughout steps (2) and (3), or all at once in step (3). For example, when the total amount of second glycol component added (supplied) to the entire preparation method is G1+G2+G3, G1, i.e., a portion of the total amount, can be added in portions in step (1) where the reaction raw materials are prepared, G2, i.e., another portion of the total amount, can be added in portions in step (2) where the first esterification reaction is carried out, and G3, i.e., another portion of the total amount, can be added in portions in step (3) where the second esterification reaction is carried out. In addition, G1, i.e., a portion of the total amount, can be added in portions in step (2) where the first esterification reaction is carried out, and G2+G3, i.e., another portion of the total amount, can be added in portions in step (3) where the second esterification reaction is carried out. In addition, G1+G2+G3, i.e., the total amount, may not be added in steps (1) and (2), but may be added all at once in step (3) where the second esterification reaction is carried out. As described above, when the second glycol component is added in portions to each reaction step or added all at once in the later reaction step, i.e., step (3), the process residence time of the second glycol component can be significantly shortened in a continuous process in which the reaction is carried out over a long period of time. As a result, thermal decomposition of the second glycol component is minimized and the production of side reaction products is reduced, allowing the preparation of a high-quality polyester resin.

[0047] According to the present invention, when the second glycol component is added in two or more portions in steps (1) to (3), the second glycol component can be added in step (3) in an amount greater than 20% by weight of the total amount of the second glycol component. Specifically, the second glycol component can be added in step (3) in an amount equivalent to 25 to 99%, 30 to 99%, 35 to 99%, 40 to 99%, 50 to 95%, or 70 to 95% by weight of the total amount of the second glycol component (total amount added throughout the entire process). Controlling the amount of the second glycol component can significantly reduce the process residence time of the second glycol component in a continuous process in which the reaction is carried out for a long period of time; thus, a high-quality polyester resin can be prepared.

[0048] The second glycol component is not particularly limited as long as it is a compound having two or more carbon atoms (particularly, 3 to 10 carbon atoms) and two hydroxy groups (OH). In particular, the second glycol component may be bis-2-hydroxyethyl terephthalate, regenerated bis-2-hydroxyethyl terephthalate, isosorbide, regenerated isosorbide, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, regenerated 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, regenerated 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexa ... The second glycol component may include at least one selected from the group consisting of cyclohexanedimethanol derivatives (e.g., 4-(hydroxymethyl)cyclohexylmethyl 4-(hydroxymethyl)cyclohexanecarboxylate; 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol, etc.), 2,2,4,4-tetramethyl-1,3-cyclobutanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymers of ethylene oxide and tetrahydrofuran, ethylene oxide-added polypropylene glycol, polycarbonate diol, polyneopentyl glycol, poly-3-methylpentanediol, and poly-1,5-pentanediol. Preferably, the second glycol component may include at least one selected from the group consisting of bis-2-hydroxyethyl terephthalate, recycled bis-2-hydroxyethyl terephthalate, isosorbide, diethylene glycol, and 1,4-cyclohexanedimethanol to obtain a high-quality polyester resin in an economical manner.

[0049] Among the second glycol components, recycled bis-2-hydroxyethyl terephthalate (r-BHET) may be obtained by depolymerization (e.g., glycolysis, hydrolysis, and methanolysis) of waste polyester resin. Such r-BHET may be added in powder form, either in portions or all at once, or dissolved in a solvent. For example, r-BHET may be added as an r-BHET solution obtained by adding r-BHET to ethylene glycol (EG) or water and mixing them at 60 to 190°C. In such cases, the concentration of r-BHET in the r-BHET solution is not particularly limited, but may be 50 to 95%.

[0050] On the other hand, according to the present invention, steps (1) to (3) can be carried out continuously, and as a result, the polyester resin can be prepared in a high yield and economical manner.

[0051] Step (4): Polycondensation reaction According to the present invention, step (4) is a step of subjecting the second reactant to polycondensation to obtain a third reactant comprising a polymer. In particular, step (4) may include charging the second reactant into a polycondensation reactor and carrying out a polycondensation reaction in the presence of a catalyst to produce a third reactant comprising a polyester (co)polymer.

[0052] The conditions under which the polycondensation reaction is carried out are not particularly limited. In particular, the temperature at which the polycondensation reaction is carried out may be 150 to 300°C, 180 to 295°C, 200 to 290°C, 230 to 285°C, or 260 to 285°C. The pressure at which the polycondensation reaction is carried out may be lower than atmospheric pressure (e.g., 1 atm) (reduced pressure). In addition, the time for which the polycondensation reaction is carried out may be 1 to 24 hours, 2 to 20 hours, 3 to 15 hours, or 4 to 10 hours. When the polycondensation reaction is carried out under the above conditions, a polyester polymer (homopolymer or copolymer) having a desired intrinsic viscosity (IV) and color can be efficiently produced, while by-products are smoothly discharged from the polycondensation reactor.

[0053] Step (4) in which a polycondensation reaction is carried out is carried out after steps (1) to (3), and may be carried out continuously together with steps (1) to (3).

[0054] Meanwhile, the present invention may further include subjecting the polyester polymer (third reactant) obtained by the polycondensation reaction in step (4) to a solid-state polymerization reaction in order to control the intrinsic viscosity (IV), molecular weight, etc. of the polyester polymer. The solid-state polymerization reaction conditions are not particularly limited and may be appropriately set depending on the intrinsic viscosity, molecular weight, etc. of the desired polyester polymer.

[0055] Step (5): Recovery and purification According to the present invention, step (5) is a step of recovering and purifying the glycol by-product formed in any one or more of steps (2) to (4). In particular, step (5) may include recovering and purifying at least one of the glycol by-product formed in the first esterification reaction, the glycol by-product formed in the second esterification reaction, and the glycol by-product formed in the polycondensation reaction to obtain a purified product.

[0056] The glycol by-product may include at least one selected from the group consisting of ethylene glycol, diethylene glycol, monohydroxyethyl terephthalate (MHET), bis-2-hydroxyethyl terephthalate (BHET), bis-2-hydroxyethyl terephthalate dimer (BHET dimer), and diethylene glycol ester (DEG ester). The glycol by-product may be recovered and then subjected to a commonly known purification process, and the purified product (e.g., ethylene glycol) obtained by the purification process may be reused as a reaction raw material in step (1). As a result, the present invention can provide a polyester resin in an economical manner.

[0057] (polyester resin) The present invention provides a polyester resin prepared by the above-described method for preparing a polyester resin. The polyester resin according to the present invention can be a homopolymer or a copolymer. In particular, the polyester resin can be selected from the group consisting of polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polyester sulfone (PES), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polybutylene adipate-co-terephthalate (PBAT), polypropylene adipate-co-terephthalate (PPAT), polycyclohexanedimethyl terephthalate (PCT), and thermoplastic polyester elastomer (TPEE).

[0058] The polyester resin according to the present invention can have high quality because it is prepared by the above-described preparation method. In particular, the polyester resin according to the present invention can have excellent color properties (transparency) and moldability (injection moldability). In particular, the polyester resin in a pellet state can have a col-b value of -4 to +3 (particularly, -3.8 to +2.8 or -3.5 to +2.5) and a delta col-b value of 0.1 or more (particularly, 0.1 to 2.5, 0.1 to 2.3, 0.4 to 2, 0.6 to 1.8, or 0.8 to 1.6).

[0059] Col-b is a color coordinate system established by the Commission International d'Eclairage (CIE), and colors are expressed as "yellow to blue complementary colors." Col-b can be measured using an UltraScan PRO (manufacturer: Hunterlab).

[0060] Delta Col-b refers to the difference in Col-b values ​​depending on whether the reactants are added in portions or all at once. A value of 0.1 or greater indicates improved color characteristics.

[0061] The polyester resin according to the present invention may have an intrinsic viscosity (IV) of 0.50 to 1.25 dL / g at 35°C. Specifically, the intrinsic viscosity of the polyester resin at 35°C may be 0.50 to 1.2 dL / g, 0.55 to 1.0 dL / g, 0.55 to 0.90 dL / g, 0.60 to 0.85 dL / g, or 0.65 to 0.80 dL / g. More specifically, the melt intrinsic viscosity (melt IV) of the polyester resin at 35°C may be 0.50 to 1.2 dL / g, 0.70 to 1.0 dL / g, or 0.75 to 0.90 dL / g. Additionally, the solid phase intrinsic viscosity (solid phase IV) of the polyester resin at 35°C may be 0.7 to 1.25 dL / g, 0.90 to 1.20 dL / g, or 1.0 to 1.15 dL / g. Melt intrinsic viscosity is the intrinsic viscosity of a polyester resin measured after polycondensation (melt polymerization) but before solid-state polymerization. Solid-state intrinsic viscosity is the intrinsic viscosity of a polyester resin measured after polycondensation (melt polymerization) and solid-state polymerization.

[0062] Intrinsic viscosity can be measured using an Ubbelohde viscometer in a thermostatic bath at 35°C. Specifically, a polyester resin is dissolved in orthochlorophenol (OCP) at 150°C at a concentration of 0.12% to obtain a solution. While maintaining the temperature of the viscosity tube of the Ubbelohde viscometer at 35°C, the time required for the OCP solvent to pass through a specific internal section of the viscosity tube (flow time) and the time required for the solution to pass through are measured to obtain a specific viscosity, which is used to calculate the intrinsic viscosity.

[0063] The polyester resin according to the present invention can be in the form of chips, pellets, or powder (particles).

[0064] (Goods) The present invention provides an article comprising the polyester resin described above. In particular, the article according to the present invention can be obtained by molding the polyester resin using a molding method such as extrusion and injection. For example, the article according to the present invention can be a film (or sheet) or a part used in the automotive, electrical, and electronics fields.

[0065] In particular, the article according to the present invention can be an injection-molded polyester product (e.g., polyester film) with excellent color properties. The injection-molded polyester product (e.g., polyester film) can have a difference (xy) between the col-L value (x) and the col-b value (y) of 89 to 94 (particularly, 90 to 94, 90.5 to 94, 91 to 94, or 92 to 94) based on a thickness of 6 mm. When the difference (xy) between the col-L value (x) and the col-b value (y) is within the above range, the injection-molded polyester product of the present invention can have excellent transparency.

[0066] Col-L represents "lightness" in the color coordinate system established by the Commission International d'Eclairage (CIE). Col-L, like col-b, can be measured using an UltraScan PRO (manufacturer: Hunterlab).

[0067] [Mode of Invention] The present invention will now be described in more detail with reference to embodiments, which are provided for illustrative purposes only and are not intended to limit the scope of the present invention.

[0068] <Preparation of polyester resin (copolymer)> [Example 1] A reaction feedstock containing recycled bis-2-hydroxyethyl terephthalate (r-BHET), terephthalic acid (TPA), ethylene glycol (EG), isosorbide (ISB), and diethylene glycol (DEG) was prepared. The reaction feedstock and other ingredients (catalyst, stabilizer, and colorant) were mixed to form a slurry and continuously fed to a continuous reactor for the first esterification. Specifically, recycled bis-2-hydroxyethyl terephthalate (r-BHET, 528.0 kg / hr), terephthalic acid (TPA, 1,380.2 kg / hr), ethylene glycol (EG, 429.6 kg / hr), isosorbide (ISB, 20.2 kg / hr), diethylene glycol (DEG, 22.0 kg / hr), Ge catalyst (1.3 kg / hr), Ti catalyst (0.19 kg / hr), phosphoric acid (0.208 kg / hr), blue toner (0.008 kg / hr), and red toner (0.002 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that could be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 0.5 kgf / cm. 2 The reaction was carried out at 255°C under a pressure of 1000kJ / cm2 for 1.5 hours to obtain the first reaction product (G / A=1.10).

[0069] Next, the first reactant was charged into a continuous reactor for second esterification equipped with a column and a condenser that can be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at a pressure of 0.5 kgf / cm. 2 The second reaction mixture was then subjected to a pressure of 1000 kJ / s at a temperature of 260°C for 7 hours to obtain a second reaction product. In this case, while the second esterification reaction was being carried out, 1,4-cyclohexanedimethanol (CHDM, 149.7 kg / hr) that had not been fed to the continuous reactor for the first esterification was continuously fed to the continuous reactor for the second esterification.

[0070] The second reactant was then added to a polycondensation reactor, and the polycondensation reaction was carried out for 7 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.70 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to have an average weight of 12 to 14 mg.

[0071] The granules thus obtained were then left to crystallize at 150°C for 1 hour and then placed in a 20-liter reactor for solid-state polymerization. The solid-state polymerization reaction was carried out under nitrogen flow at a rate of 50 L / min. The temperature of the solid-state polymerization reactor was increased from room temperature to 190°C at a rate of 40°C / hr and maintained at 190°C. The solid-state polymerization reaction was carried out until the intrinsic viscosity (IV) of the granules in the solid-state polymerization reactor reached 1.15 dL / g, thereby preparing polyester resin (copolymer) pellets.

[0072] Meanwhile, glycol by-products formed from the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0073] [Example 2] A reaction mixture containing terephthalic acid (TPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), diethylene glycol (DEG), and cyclohexanedimethanol derivatives (CHDM derivatives) was prepared. The reaction mixture and other raw materials (catalyst, stabilizer, and colorant) were continuously fed into a continuous reactor for the first esterification. Specifically, terephthalic acid (TPA, 1,495.0 kg / hr), ethylene glycol (EG, 238.2 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 713.2 kg / hr), diethylene glycol (DEG, 9.7 kg / hr), cyclohexanedimethanol derivatives (CHDM derivatives, 40.0 kg / hr), zinc acetate (0.18 kg / hr), Ge catalyst (2.7 kg / hr), Ti catalyst (0.19 kg / hr), phosphoric acid (0.208 kg / hr), blue toner (0.005 kg / hr), and red toner (0.001 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that could be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 2 kgf / cm. 2 The reaction was carried out at 275°C under a pressure of 1000kJ / cm2 for 2.5 hours to obtain the first reaction product (G / A=0.95).

[0074] Next, the first reactant was introduced into a continuous reactor for the second esterification, which was equipped with a column and a condenser that could be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at a flow rate of 2 kgf / cm. 2 The second reaction mixture was then subjected to a pressure of 1000 kJ / s at a temperature of 255°C for 5 hours to obtain a second reaction product. In this case, while the second esterification reaction was being carried out, isosorbide (ISB, 175.3 kg / hr) that had not been fed to the continuous reactor for the first esterification was continuously fed to the continuous reactor for the second esterification.

[0075] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 10 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.70 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of about 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0076] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0077] [Example 3] A reaction feedstock containing recycled bis-2-hydroxyethyl terephthalate (r-BHET), terephthalic acid (TPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), isosorbide (ISB), and diethylene glycol (DEG) was prepared. The reaction feedstock and other raw materials (catalyst, stabilizer, and colorant) were mixed in a slurry and continuously fed to a continuous reactor for the first esterification. Specifically, recycled bis-2-hydroxyethyl terephthalate (r-BHET, 112.0 kg / hr), terephthalic acid (TPA, 1,390.9 kg / hr), ethylene glycol (EG, 47.4 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 889.1 kg / hr), isosorbide (ISB, 226.6 kg / hr), diethylene glycol (DEG, 9.3 kg / hr), zinc acetate (0.88 kg / hr), Ge catalyst (13.3 kg / hr), phosphoric acid (0.042 kg / hr), blue toner (0.006 kg / hr), and red toner (0.002 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that can be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 1 kgf / cm. 2 The reaction was carried out at 275°C under a pressure of 1000kJ / 2000kcal for 1.5 hours to obtain the first reaction product (G / A=1.07).

[0078] Next, the first reactant was introduced into a continuous reactor for second esterification equipped with a column and a condenser that can be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at 1 kgf / cm 2 The second reaction mixture was then subjected to a pressure of 1000 kJ / min at a temperature of 265°C for 4 hours to obtain a second reaction product. In this case, while the second esterification reaction was being carried out, isosorbide (ISB, 151.1 kg / hr) was continuously fed in a divided (distributed) manner to the continuous reactor for the second esterification.

[0079] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 6 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.75 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of about 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0080] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0081] [Example 4] A reaction mixture containing terephthalic acid (TPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), diethylene glycol (DEG), and cyclohexanedimethanol derivatives (CHDM derivatives) was prepared. The reaction mixture and other raw materials (catalyst, stabilizer, and colorant) were continuously fed into a continuous reactor for the first esterification. Specifically, terephthalic acid (TPA, 1,633.4 kg / hr), ethylene glycol (EG, 390.5 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 354.2 kg / hr), diethylene glycol (DEG, 15.6 kg / hr), cyclohexanedimethanol derivatives (CHDM derivatives, 86.2 kg / hr), Ge catalyst (1.3 kg / hr), phosphoric acid (0.208 kg / hr), blue toner (0.010 kg / hr), and red toner (0.004 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that can be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 0.5 kgf / cm. 2 The reaction was carried out at 255°C under a pressure of 1000kJ for 2.5 hours to obtain the first reaction product (G / A=0.97).

[0082] Next, the first reactant was charged into a continuous reactor for second esterification equipped with a column and a condenser that can be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at a pressure of 0.5 kgf / cm. 2 The second reaction mixture was then subjected to a pressure of 1000 kJ / min at a temperature of 260°C for 8 hours to obtain a second reaction product. In this case, while the second esterification reaction was being carried out, diethylene glycol (DEG, 140.8 kg / hr) was continuously fed in a divided (distributed) manner to the continuous reactor for the second esterification.

[0083] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 9 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure, until the intrinsic viscosity (IV) reached 0.77 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of about 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0084] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0085] [Example 5] A reaction feedstock containing recycled bis-2-hydroxyethyl terephthalate (r-BHET), terephthalic acid (TPA), isophthalic acid (IPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), and diethylene glycol (DEG) was prepared. The reaction feedstock and other ingredients (catalyst, stabilizer, and colorant) were mixed in a slurry and continuously fed to a continuous reactor for the first esterification. Specifically, recycled bis-2-hydroxyethyl terephthalate (r-BHET, 955.3 kg / hr), terephthalic acid (TPA, 936.5 kg / hr), isophthalic acid (IPA, 624.3 kg / hr), ethylene glycol (EG, 104.9 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 118.5 kg / hr), diethylene glycol (DEG, 19.9 kg / hr), zinc acetate (0.58 kg / hr), Ti catalyst (0.19 kg / hr), phosphoric acid (2.083 kg / hr), and blue toner (0.010 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that could be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 3 kgf / cm. 2 The reaction was carried out at 255°C under a pressure of 1000kJ for 1 hour to obtain the first reaction product (G / A=1.09).

[0086] Next, the first reactant was charged into a continuous reactor for second esterification equipped with a column and a condenser that can be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at 3 kgf / cm 2 The second reaction mixture was then subjected to a pressure of 1000 kJ / min at a temperature of 260°C for 5 hours to obtain a second reaction product. In this case, while the second esterification reaction was being carried out, 1,4-cyclohexanedimethanol (CHDM, 355.4 kg / hr) was continuously fed in a divided (distributed) manner to the continuous reactor for the second esterification.

[0087] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 4 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.65 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of about 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0088] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0089] [Example 6] A reaction feedstock containing recycled bis-2-hydroxyethyl terephthalate (r-BHET), terephthalic acid (TPA), isophthalic acid (IPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), and diethylene glycol (DEG) was prepared. The reaction feedstock and other ingredients (catalyst, stabilizer, and colorant) were mixed in a slurry and continuously fed to a continuous reactor for the first esterification. Specifically, recycled bis-2-hydroxyethyl terephthalate (r-BHET, 971.2 kg / hr), terephthalic acid (TPA, 952.1 kg / hr), isophthalic acid (IPA, 634.7 kg / hr), ethylene glycol (EG, 4.0 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 688.3 kg / hr), diethylene glycol (DEG, 10.1 kg / hr), zinc acetate (0.29 kg / hr), Ge catalyst (1.3 kg / hr), blue toner (0.010 kg / hr), and red toner (0.004 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that can be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 0.5 kgf / cm. 2 The reaction was carried out at 255°C under a pressure of 1000kJ for 3 hours to obtain the first reaction product (G / A=0.92).

[0090] Next, the first reactant was charged into a continuous reactor for second esterification equipped with a column and a condenser that can be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at 3 kgf / cm 2 The second reaction mixture was then subjected to a pressure of 1000 kJ / s at a temperature of 260°C for 5 hours to obtain a second reaction product. In this case, while the second esterification reaction was being carried out, isosorbide (ISB, 718.9 kg / hr) that had not been fed into the continuous reactor for the first esterification was continuously fed into the continuous reactor for the second esterification.

[0091] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 4 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.68 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of about 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0092] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0093] [Example 7] A reaction feedstock containing recycled bis-2-hydroxyethyl terephthalate (r-BHET), terephthalic acid (TPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), and diethylene glycol (DEG) was prepared. The reaction feedstock and other ingredients (catalyst, stabilizer, and colorant) were mixed to form a slurry and continuously fed to a continuous reactor for the first esterification. Specifically, recycled bis-2-hydroxyethyl terephthalate (r-BHET, 438.0 kg / hr), terephthalic acid (TPA, 667.9 kg / hr), ethylene glycol (EG, 188.9 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 198.6 kg / hr), diethylene glycol (DEG, 12.2 kg / hr), zinc acetate (0.11 kg / hr), Ge catalyst (0.8 kg / hr), phosphoric acid (0.025 kg / hr), blue toner (0.004 kg / hr), and red toner (0.001 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that could be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 0.5 kgf / cm. 2 The reaction was carried out at 255°C under a pressure of 1000kJ for 3 hours to obtain the first reaction product (G / A=1.39).

[0094] Next, the first reactant was introduced into a continuous reactor for second esterification equipped with a column and a condenser that can be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at 1 kgf / cm 2 The second reaction mixture was then subjected to a pressure of 1000 kJ / min at a temperature of 265°C for 5 hours to obtain a second reaction product. In this case, while the second esterification reaction was being carried out, 1,4-cyclohexanedimethanol (CHDM, 49.7 kg / hr) was continuously fed in a divided (distributed) manner to the continuous reactor for the second esterification.

[0095] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 5 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.70 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of about 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0096] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0097] [Example 8] A reaction feedstock containing recycled bis-2-hydroxyethyl terephthalate (r-BHET), terephthalic acid (TPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), and diethylene glycol (DEG) was prepared. The reaction feedstock and other ingredients (catalyst, stabilizer, and colorant) were mixed to form a slurry and continuously fed to a continuous reactor for the first esterification. Specifically, recycled bis-2-hydroxyethyl terephthalate (r-BHET, 485.6 kg / hr), terephthalic acid (TPA, 1,269.5 kg / hr), ethylene glycol (EG, 148.0 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 688.3 kg / hr), diethylene glycol (DEG, 10.1 kg / hr), zinc acetate (0.29 kg / hr), Ge catalyst (1.3 kg / hr), blue toner (0.010 kg / hr), and red toner (0.004 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that could be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 0.5 kgf / cm. 2 The reaction was carried out at 255°C under a pressure of 1000 kJ for 3 hours to obtain the first reaction product (G / A=0.98).

[0098] Next, the first reactant was charged into a continuous reactor for second esterification equipped with a column and a condenser that can be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at 3 kgf / cm 2 The second reaction mixture was then subjected to a pressure of 1000 kJ / s at a temperature of 260°C for 5 hours to obtain a second reaction product. In this case, while the second esterification reaction was being carried out, ethylene glycol (EG, 93 kg / hr) was continuously fed in a divided (distributed) manner to the continuous reactor for the second esterification.

[0099] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 4 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.68 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of about 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0100] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0101] [Comparative Example 1] A reaction mixture containing recycled bis-2-hydroxyethyl terephthalate (r-BHET), terephthalic acid (TPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), isosorbide (ISB), and cyclohexanedimethanol derivatives (CHDM derivatives) was prepared. The reaction mixture and other raw materials (catalyst, stabilizer, and colorant) were continuously fed into a continuous reactor for the first esterification. Specifically, recycled bis-2-hydroxyethyl terephthalate (r-BHET, 139.1 kg / hr), terephthalic acid (TPA, 818.2 kg / hr), ethylene glycol (EG, 176.6 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 433.8 kg / hr), isosorbide (ISB, 159.9 kg / hr), cyclohexanedimethanol derivatives (CHDM derivatives, 24.0 kg / hr), Ge catalyst (1.6 kg / hr), Ti catalyst (0.11 kg / hr), phosphoric acid (0.125 kg / hr), blue toner (0.003 kg / hr), and red toner (0.001 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that can be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 2 kgf / cm. 2The reaction was carried out at 250°C under a pressure of 1000kJ for 2 hours to obtain the first reaction product (G / A=1.30).

[0102] Next, the first reactant was introduced into a continuous reactor for the second esterification, which was equipped with a column and a condenser that could be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at a flow rate of 2 kgf / cm. 2 The reaction was carried out at a temperature of 255°C under a pressure of 1000 kJ for 5 hours to obtain the second reaction product.

[0103] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 10 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.80 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of approximately 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0104] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0105] Comparative Example 2 A reaction feedstock containing recycled bis-2-hydroxyethyl terephthalate (r-BHET), terephthalic acid (TPA), ethylene glycol (EG), 1,4-cyclohexanedimethanol (CHDM), isosorbide (ISB), and diethylene glycol (DEG) was prepared. The reaction feedstock and other raw materials (catalyst, stabilizer, and colorant) were mixed in a slurry and continuously fed to a continuous reactor for the first esterification. Specifically, recycled bis-2-hydroxyethyl terephthalate (r-BHET, 437.0 kg / hr), terephthalic acid (TPA, 666.5 kg / hr), ethylene glycol (EG, 73.5 kg / hr), 1,4-cyclohexanedimethanol (CHDM, 413.0 kg / hr), isosorbide (ISB, 279.1 kg / hr), diethylene glycol (DEG, 6.1 kg / hr), zinc acetate (0.11 kg / hr), Ge catalyst (0.8 kg / hr), phosphoric acid (0.025 kg / hr), blue toner (0.004 kg / hr), and red toner (0.001 kg / hr) were continuously fed into a continuous reactor for the first esterification equipped with a column and a condenser that could be cooled with water. The first esterification reaction (ES-1) was carried out at a flow rate of 1 kgf / cm. 2 The reaction was carried out at 260°C under a pressure of 1000kJ / cm2 for 2.5 hours to obtain the first reaction product (G / A=1.25).

[0106] Next, the first reactant was introduced into a continuous reactor for second esterification equipped with a column and a condenser that can be cooled with water, and the second esterification reaction (ester exchange reaction) (ES-2) was carried out at 1 kgf / cm 2 The reaction was carried out at a temperature of 265°C under a pressure of 1000 kJ for 5 hours to obtain the second reaction product.

[0107] The second reactant was then charged into a polycondensation reactor, and the polycondensation reaction was carried out for 5 hours while maintaining the pressure in the polycondensation reactor at a pressure lower than atmospheric pressure until the intrinsic viscosity (IV) reached 0.70 dL / g. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached the desired level, the mixture (third reactant) was discharged from the reactor to form strands, which were solidified with a cooling liquid and then granulated to an average weight of about 12 to 14 mg to prepare polyester resin (copolymer) pellets.

[0108] Meanwhile, glycol by-products formed in the first esterification reaction, the second esterification reaction, and / or the polycondensation reaction were recovered through columns and condensers in each process and reused as reaction raw materials through separate purification processes.

[0109] [Test Example 1] The rate of change in molecular weight (M R C) was calculated according to the following formula 1. The results are shown in Table 1 below. Here, the number average molecular weight of the oligomer contained in each reaction product was analyzed by gel permeation chromatography (GPC) using polystyrene as a standard substance. [Formula 1] M RC =(Mn1 / Mn2)×100 [In the formula, Mn1 is the number average molecular weight of the oligomer contained in the first reaction product obtained by the first esterification reaction, and Mn2 is the number average molecular weight of the oligomer contained in the second reaction product obtained by the second esterification reaction]. [Table 1]

[0110] Referring to Table 1 above, when the second glycol component (CHDM, ISB, DEG, or EG) was added in portions to the first and second esterification reactions or all at once to the second esterification reaction, the residence time of the second glycol component was shortened, thereby reducing heat-induced side reactions, and as a result, oligomers were successfully formed with little change in molecular weight.

[0111] Preparation of Polyester Articles [Preparation Examples 1 to 8 and Comparative Preparation Examples 1 and 2] The polyester resin pellets obtained in Examples 1 to 8 and Comparative Examples 1 and 2 were injection molded by a conventional method to prepare polyester injection samples having a thickness of 6 mm (6T).

[0112] [Test Example 2] The color of the polyester resin pellets obtained in Examples 1 to 8 and Comparative Examples 1 to 2, as well as the injection-molded polyester samples obtained in Preparation Examples 1 to 8 and Comparative Preparation Examples 1 to 2, was analyzed. The results are shown in Table 2 below. Specifically, the color and brightness of the pellets and injection-molded samples were measured using a Varian Cary 5 UV / Vis / NIR spectrophotometer equipped with a diffuse reflection accessory. Transmission data was then acquired at a 2° observation angle using Illuminant D65. This data was processed by a color analyzer using Grams / 32 software to calculate Hunter Lab values. Here, pellet delta col-b refers to the difference between the col-b value of pellets obtained by adding the second glycol component in portions or all at once and the col-b value of pellets obtained by adding the second glycol component all at once at the beginning of the reaction. [Table 2]

[0113] Referring to Table 2 above, the polyester resin pellets obtained according to the present invention and the injection molded polyester samples prepared therewith had excellent color stability and therefore high quality.

Claims

1. 1. A method for preparing a polyester resin, comprising: (1) preparing a reaction feedstock comprising a first glycol component and an acid component; (2) subjecting the reaction raw material to a first esterification reaction to obtain a first reactant; (3) subjecting the first reactant to a second esterification reaction to obtain a second reactant; Including, at least one second glycol component having a carbon number of 2 or more is added in portions throughout steps (1) to (3), or in portions throughout steps (2) and (3), or all at once in step (3); method.

2. The second glycol component is bis-2-hydroxyethyl terephthalate, regenerated bis-2-hydroxyethyl terephthalate, isosorbide, regenerated isosorbide, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, regenerated 1,4-cyclohexanedimethanol, 2-methyl-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, regenerated 2,2-dimethyl-1,3-propanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol 2. The method for preparing the polyester resin of claim 1, wherein the hydroxybenzoate is selected from the group consisting of 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, cyclohexanedimethanol derivatives, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, copolymers of ethylene oxide and tetrahydrofuran, ethylene oxide-added polypropylene glycol, polycarbonate diol, polyneopentyl glycol, poly-3-methylpentanediol, and poly-1,5-pentanediol.

3. 3. The method for preparing the polyester resin of claim 2, wherein the second glycol component is selected from the group consisting of bis-2-hydroxyethyl terephthalate, recycled bis-2-hydroxyethyl terephthalate, isosorbide, diethylene glycol, and 1,4-cyclohexanedimethanol.

4. 2. The method for preparing the polyester resin according to claim 1, wherein the molar ratio of (the molar ratio of the first glycol component + the molar ratio of the second glycol component) / acid component (G / A) in the first esterification reaction in step (2) is 1.2 or less.

5. 10. The method for preparing a polyester resin according to claim 1, wherein the first esterification reaction in step (2) is carried out at 120 to 280°C.

6. 10. The method for preparing a polyester resin according to claim 1, wherein the second esterification reaction in step (3) is carried out at 150 to 280°C.

7. The rate of change in molecular weight of the reactants (M ＲＣ ) is represented by the following formula 1: [Formula 1] M ＲＣ =(Mn １ / Mn ２ )×100 [In the formula, Mn １ is the number average molecular weight of the oligomer contained in the first reactant, and Mn ２ is the number average molecular weight of the oligomer contained in the second reactant.

2. The method for preparing the polyester resin of claim 1, wherein the polyester resin has a viscosity of 90% or more according to the following formula:

8. 10. The method of preparing the polyester resin of claim 1, further comprising the step of: (4) subjecting the second reactant to polycondensation to obtain a third reactant comprising a polymer.

9. 9. The method for preparing the polyester resin of claim 8, further comprising the step of: (5) recovering and purifying the glycol by-product formed in any one or more of steps (2) through (4).

10. 2. The method for preparing the polyester resin of claim 1, wherein steps (1) to (3) are carried out sequentially.

11. A polyester resin prepared by the method of any one of claims 1 to 10.

12. 12. The polyester resin of claim 11, in pellet form, having a col-b value of -4 to +3 and a delta col-b value of 0.1 or greater.

13. An article comprising the polyester resin of claim 11.

14. 14. The article of claim 13, wherein the article is an injection molded polyester article, and the injection molded polyester article has a difference between the col-L value and the col-b value of 89 to 94 based on a thickness of 6 mm.

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