KR101842247B1 - Polyester resin and preparation method thereof - Google Patents

Abstract

According to an embodiment of the present invention, the present invention relates to a polyester resin for calendaring, comprising a dicarboxylic acid repeating unit and a diol repeating unit. The diol repeating unit comprises greater than 30 to less than or equal to 90 mole% of a neopentyl glycol residue, based on the total moles of the diol repeating unit. The diol repeating unit does not contain an alicyclic diol residue, and the intrinsic viscosity (IV) of the polyester resin is 0.68 to 3.0 dl/g. The polyester resin for calendering consumes low calories for crystallization, ensures excellent processability, and also enables production of economically feasible and eco-friendly polyester resins.

Description

[0001] POLYESTER RESIN AND PREPARATION METHOD THEREOF [0002]

The present invention relates to a polyester resin which is low in crystallization heat and excellent in calendar processability as well as economical and environmentally friendly, and a method for producing the same.

The calendering process is a process of forming a film, a sheet or the like using a calender, that is, a rolling machine in which a plurality of heating rolls are arranged. The calendering process is one of the representative methods of making films and sheets because it is faster in production speed and easier to process with thinner thickness than extrusion process.

Of the commonly used resins, the PET resin has excellent physical properties with respect to price, but has a problem that calendering workability is poor. In the case of the PETG resin, the calendering process can be applied, but its use is limited due to its high price. When the PETG resin is manufactured into a film, its surface strength is low and it is difficult to use it as a deco sheet or the like. In addition, in the case of PVC, calendering workability is excellent, but it is not environmentally friendly and recycling is difficult. Thus, there has been a need for a polymeric resin that can be used in a calendering process, but which can overcome the disadvantages of the resins.

For example, Korean Patent Publication No. 2014-0109506 discloses a polyester composition for calendering comprising a terephthalic acid residue, a 1,4-cyclohexane dimethanol residue, and an ethylene glycol residue.

Korea Patent Publication No. 2014-0109506

However, when a film is produced by calendering a polyester resin containing an alicyclic diol residue such as a cyclohexane dimethanol residue, there is a problem that the surface hardness and chemical resistance of the film are degraded (Korean Patent Publication No. 2014-0109506 See also

Therefore, the object of the embodiment is to provide a polyester resin which is low in crystallization heat and excellent in calendar processability, economical and environmentally friendly, and a method for producing the same.

In order to achieve the above object,

1. A calendering polyester resin comprising a dicarboxylic acid repeating unit and a diol repeating unit,

Wherein the diol repeat unit comprises a neopentyl glycol (NPG) residue in an amount of greater than 30 to less than 90 mole percent, based on the total moles of the diol repeat units,

Wherein the diol repeat unit does not comprise an alicyclic diol residue,

Wherein the polyester resin has an intrinsic viscosity (IV) of 0.68 to 3.0 dl / g,

A polyester resin for calendering is provided.

Further, in one embodiment,

Mixing the mixture so that the molar ratio of the dicarboxylic acid component and the diol component is 1: 1.05 to 1: 3.0, and performing the esterification reaction; And

And polycondensation of the esterified product, the method comprising the steps of:

Wherein the diol component comprises greater than 30 to less than 90 mole percent neopentyl glycol based on the total moles of the diol component,

Wherein the diol component does not comprise an alicyclic diol,

Wherein the polyester resin has an intrinsic viscosity (IV) of 0.68 to 3.0 dl / g,

A method for producing a polyester resin for calendering is provided.

The calendering polyester resin according to the embodiment has a specific intrinsic viscosity and a low crystallization heat quantity, so that calendering workability is excellent.

Further, the polyester resin according to the embodiment is economical and functions as an eco-friendly material, and thus can be utilized in various ways.

Further, according to the process for producing a polyester resin for calendering according to the embodiment, it is possible to produce a polyester resin which is low in crystallization heat quantity, excellent in calendar workability, economical and environmentally friendly.

The examples provide polyester resins that can be used in the calendering process and methods of making the same.

The calendering polyester resin according to one embodiment is a calendering polyester resin comprising a dicarboxylic acid repeating unit and a diol repeating unit,

Wherein the diol repeat unit comprises a neopentyl glycol (NPG) residue in an amount of greater than 30 to less than 90 mole percent, based on the total moles of the diol repeat units,

Wherein the diol repeat unit does not comprise an alicyclic diol residue,

And the polyester resin has an intrinsic viscosity (IV) of 0.68 to 3.0 dl / g.

The dicarboxylic acid repeating unit may be at least one selected from the group consisting of terephthalic acid (TPA), isophthalic acid (IPA), naphthalene dicarboxylic acid (NDC), cyclohexanedicarboxylic acid (CHDA), succinic acid, glutaric acid, , Azelaic acid, sebacic acid, decanedicarboxylic acid, 2,5-furandicarboxylic acid, 2,5-thiopendicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-bibenzoic acid And derivatives thereof, or any combination thereof.

Specifically, the dicarboxylic acid repeating unit may include, but is not limited to, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, or any combination thereof.

More specifically, the dicarboxylic acid repeating unit may include, but is not limited to, a terephthalic acid residue.

The dicarboxylic acid repeating unit may be composed of terephthalic acid residues, but is not limited thereto.

The diol repeat unit comprises more than 30 to less than 90 mole percent neopentyl glycol moieties, based on the total moles of the diol repeat units. Specifically, the diol repeating unit may contain more than 30 to less than 80 mole% of neopentyl glycol residues, based on the total moles of the diol repeat units. More specifically, the diol repeat unit may comprise more than 30 to less than 70 mole percent neopentyl glycol residues, based on the total moles of the diol repeat units. For example, the diol repeat unit may comprise more than 30 to less than 60 mole percent neopentyl glycol moieties, based on the total moles of the diol repeat units.

When the content of the neopentyl glycol residue is within the above range, the processability due to crystallization is excellent and it is easy to obtain a desired intrinsic viscosity. In addition, the resin has excellent color characteristics and mechanical properties. In particular, when it exceeds 90 mol%, it is difficult to increase the intrinsic viscosity by more than a certain level, so that the mechanical properties may become weak.

The diol repeating unit may be selected from the group consisting of ethylene glycol (EG), diethylene glycol (DEG), (1,3-propanediol, 1,2-octanediol, Butanediol, 1,4-butanediol, 1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2- Pentanediol, 1,1-dimethyl-1,5-pentanediol, polyether glycol (e.g., PTMEG, PEG, PPG) Lt; RTI ID = 0.0 > a < / RTI >

Specifically, the diol repeating unit may further include residues of ethylene glycol, diethylene glycol, polyether glycol, or a combination thereof, but is not limited thereto.

More specifically, the diol repeating unit may further include an ethylene glycol residue, but is not limited thereto.

The diol repeat unit may further comprise a linear diol residue. In the case of producing a film or sheet by calendaring a polyester resin further containing linear diol residues, since the packing is well performed, the film can have excellent chemical resistance and surface strength.

The diol repeat unit does not include an alicyclic diol residue. For example, the diol repeat unit does not include a cyclohexane dimethanol (CHDM) moiety.

When the film or sheet is produced by calendaring a polyester resin in which the diol repeating unit comprises an alicyclic diol residue, the packing is not made well due to the bulky structure of the alicyclic diol, The surface strength may be lowered. In addition, since the dimensional stability is poor, expansion of the application may be difficult.

Wherein the polyester resin for calendering comprises a dicarboxylic acid repeating unit and a diol repeating unit, the dicarboxylic acid repeating unit is composed of terephthalic acid residue, and the diol repeating unit is (i) a neopentyl glycol residue and ) Ethylene glycol, diethylene glycol, or combinations thereof. Specifically, the dicarboxylic acid repeating unit is composed of a terephthalic acid residue, and the diol repeating unit is composed of (i) a neopentyl glycol residue and (ii) a residue of ethylene glycol.

Wherein the dicarboxylic acid repeating unit in the calendering polyester resin comprises a terephthalic acid residue and the diol repeating unit is a residue of (i) a neopentyl glycol residue and (ii) a residue of ethylene glycol, diethylene glycol, or a combination thereof , The whitening phenomenon is reduced, the haze is as low as 8%, and the dimensional stability is excellent.

The intrinsic viscosity (IV) of the polyester resin is 0.68 to 3.0 dl / g. Specifically, the intrinsic viscosity (IV) of the polyester resin is 0.7 to 0.9 dl / g. More specifically, the polyester resin has an intrinsic viscosity (IV) of 0.7 to 0.8 dl / g. For example, the intrinsic viscosity (IV) of the polyester resin may be 0.72 to 0.78 dl / g, but is not limited thereto.

When the intrinsic viscosity of the polyester resin is in the above range, calendering workability is excellent, the kinematic viscosity retention ratio in the calendering step is excellent, and the thickness uniformity of the sheet and film is excellent.

The polyester resin has a process index of greater than 1.0 and less than or equal to 1.7 as defined by the following formula:

<Formula 1>

Process index = {(mol% of diol residue other than ethylene glycol based on the total moles of diol repeating units) / 100} + intrinsic viscosity (dl / g) of polyester resin.

The process index is the sum of the molar% content of the diol residue other than ethylene glycol and the intrinsic viscosity of the polyester resin, and corresponds to an index capable of exhibiting calendar processability.

Specifically, the process index of the polyester resin may be more than 1.0 but not more than 1.55, but is not limited thereto.

More specifically, the process index of the polyester resin may be more than 1.0 but less than 1.4, but is not limited thereto.

When the polyester process index is in the above range, the sheet is excellent in transparency, thickness uniformity and dimensional stability, and is suitable for calendering.

The method for producing a polyester resin for calendering according to another embodiment,

Mixing the mixture so that the molar ratio of the dicarboxylic acid component and the diol component is 1: 1.05 to 1: 3.0, and performing the esterification reaction; And

And polycondensation of the esterified product, the method comprising the steps of:

Wherein the diol component comprises greater than 30 to less than 90 mole percent neopentyl glycol based on the total moles of the diol component,

Wherein the diol component does not comprise an alicyclic diol,

The polyester resin has an intrinsic viscosity (IV) of 0.68 to 3.0 dl / g.

Wherein the dicarboxylic acid component is selected from the group consisting of terephthalic acid (TPA), isophthalic acid (IPA), naphthalene dicarboxylic acid (NDC), cyclohexanedicarboxylic acid (CHDA), succinic acid, glutaric acid, orthophthalic acid, Azelaic acid, sebacic acid, decanedicarboxylic acid, 2,5-furandicarboxylic acid, 2,5-thiopendicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'- Derivatives thereof, or any combination thereof.

Specifically, the dicarboxylic acid component may include, but is not limited to, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, or any combination thereof.

More specifically, the dicarboxylic acid component may include, but is not limited to, terephthalic acid.

The dicarboxylic acid component may be composed of terephthalic acid, but is not limited thereto.

The diol component comprises greater than 30 to less than 90 mole percent neopentyl glycol based on the total moles of the diol component. In particular, the diol component may comprise from greater than 30 to less than 80 mole percent neopentyl glycol, based on the total moles of the diol component. More specifically, the diol component may comprise more than 30 to less than 70 mole percent neopentyl glycol, based on the total moles of the diol component. For example, the diol component may comprise more than 30 to less than 60 mole percent neopentyl glycol, based on the total moles of the diol component.

The content of the neopentyl glycol may be an amount approximate to that of the neopentyl glycol residue in the polyester resin finally prepared. For example, to prepare a polyester resin containing about 35 mole percent neopentyl glycol moieties based on the total moles of diol repeat units, about 35 mole percent of the diol component, based on the total moles of the diol component, .

When the content of the neopentyl glycol component is within the above range, the polyester resin produced by the above production method is excellent in processability due to crystallization and is easy to obtain desired intrinsic viscosity. In addition, the resin has excellent color characteristics and mechanical properties. In particular, when it exceeds 90 mol%, it is difficult to increase the intrinsic viscosity by more than a certain level, so that the mechanical properties may become weak.

The diol component may be selected from the group consisting of ethylene glycol (EG), diethylene glycol (DEG), (1,3-propanediol, 1,2-octanediol, Butanediol, 1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2- Pentanediol, 1,1-dimethyl-1,5-pentanediol, polyether glycol (e.g., PTMEG, PEG, PPG) Combinations may be included.

Specifically, the diol component may further include, but is not limited to, ethylene glycol, diethylene glycol, polyether glycol, or a combination thereof.

More specifically, the diol component may further include, but is not limited to, ethylene glycol.

The diol component may further comprise a linear diol. In the case of producing a polyester resin by further including a linear diol and calendering the polyester resin to prepare a film or sheet, since the packing is well performed, the film can have excellent chemical resistance and surface strength.

The diol component does not include an alicyclic diol. For example, the diol component does not include cyclohexane dimethanol (CHDM).

When the polyester resin is prepared by including the alicyclic diol as the diol component and the film or sheet is produced by calendaring the polyester resin thus prepared, the packing is well formed due to the bulky structure of the alicyclic diol And the chemical resistance and surface strength of the film may be lowered.

Wherein the dicarboxylic acid component is composed of terephthalic acid and the diol component is composed of (i) neopentyl glycol and (ii) ethylene glycol, diethylene glycol, or a combination thereof. . Specifically, the dicarboxylic acid component may be composed of terephthalic acid, and the diol component may be composed of (i) neopentyl glycol and (ii) ethylene glycol.

In the case of producing a polyester resin for calendering by using the above-described components, the polyester resin is economical in terms of cost, and the produced polyester resin is eco-friendly, easy to recycle, and excellent in dimensional stability.

The acrylic resin is not included in the production of the polyester resin for calendering. In the case of reacting with the acrylic compound, an unmelted gel may be generated.

The intrinsic viscosity (IV) of the polyester resin produced through the above-mentioned production method of the polyester resin is 0.68 to 3.0 dl / g. Specifically, the intrinsic viscosity (IV) of the polyester resin is 0.7 to 0.9 dl / g. More specifically, the polyester resin has an intrinsic viscosity (IV) of 0.7 to 0.8 dl / g. For example, the intrinsic viscosity (IV) of the polyester resin may be 0.72 to 0.78 dl / g, but is not limited thereto.

When the polyester resin is produced by using the above-mentioned components and their contents, the intrinsic viscosity in the above range can be easily obtained.

When the intrinsic viscosity of the polyester resin is in the above range, calendering workability is excellent, the kinematic viscosity retention ratio in the calendering step is excellent, and the thickness uniformity of the sheet and film is excellent.

In the esterification step of the polyester resin production method, the esterification reaction is carried out by mixing the dicarboxylic acid component and the diol component at a molar ratio of 1: 1.05 to 1: 3.0. Specifically, the esterification reaction is carried out by mixing the dicarboxylic acid component and the diol component in a molar ratio of 1: 1.05 to 1: 2.0. More specifically, the esterification reaction is carried out by mixing the dicarboxylic acid component and the diol component in a molar ratio of 1: 1.05 to 1: 1.5.

When the molar ratio of the dicarboxylic acid component and the diol component is within the above range, the esterification reaction proceeds stably, a sufficient ester oligomer can be formed, and the neopentyl glycol component may be suitable to be expressed.

The polycondensation step in the production method of the polyester resin is carried out at a temperature of 230 to 270 DEG C and a pressure of 0.1 to 3.0 kg / cm &lt; ² &gt;. Specifically, the polycondensation step in the production method of the polyester resin is carried out at a temperature of 240 to 295 DEG C and a pressure of 0.2 to 2.9 kg / cm &lt; ^{2 &} gt ;.

The polycondensation step may be carried out in the presence of a polycondensation catalyst, a stabilizer, a colorant, a dispersant, an antiblocking agent, an electrostatic agent, an antistatic agent, an antioxidant, a heat stabilizer, a UV blocking agent, , And the additive may be included to the extent that the effect of the embodiment is not impaired.

The polycondensation step can be carried out in the presence of a polycondensation catalyst.

The polycondensation catalyst may include, but is not limited to, alkali metals, alkaline earth metals, antimony, titanium, manganese, cobalt, cerium, germanium, or any combination thereof. Specifically, as the polycondensation catalyst, an antimony compound may be used.

The polycondensation catalyst is present in an amount of 50 to 1,000 ppm based on the total weight of the polyester resin. Specifically, the polycondensation catalyst may be present in an amount of 50 to 500 ppm based on the total weight of the polyester resin.

When the content of the polycondensation catalyst is in the above range, the polycondensation reaction rate can be increased, side reactions can be suppressed, and excellent transparency can be obtained.

The polycondensation step can be carried out in the presence of a stabilizer.

The stabilizer may include a phosphorus stabilizer. The phosphorus stabilizer may include, but is not limited to, phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triethyl phosphonoacetate, hindered phenol, or any combination thereof.

The stabilizer is present in an amount of 3,000 ppm or less based on the total weight of the polyester resin. Specifically, the stabilizer may be present at 1 to 2,500 ppm based on the total weight of the polyester resin.

The polycondensation step may be carried out in the presence of a coloring agent.

The color developer may include, but is not limited to, cobalt acetate, cobalt propionate, an organic compound colorant, an inorganic compound colorant, a dye, or any combination thereof. Specifically, the color developer may be cobalt acetate, cobalt propionate, an inorganic compound colorant, or any combination thereof.

The color developer is present in an amount of 1 to 500 ppm based on the total weight of the polyester resin. Specifically, the coloring agent may be present in an amount of 1 to 200 ppm based on the total weight of the polyester resin.

The above contents will be described in more detail by the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the examples.

[ Example ]

Example  One : For calendering  Production of polyester resin

A copolymerized polyester resin was prepared using the components and contents shown in Table 1 below.

First, a 30 L reactor equipped with a stirrer and an outlet condenser was charged with 20 kg of the final polymer as a base so that the molar ratio of the diacid component to the diol component was 1: 1.35 as shown in the following Table 1, The pressure was increased to 2.0 kg / cm &lt; ² &gt;, and the temperature of the reactor was gradually increased to 255 DEG C, and the reaction was carried out. The resulting water was discharged out of the system and esterified. When the generation and discharge of water were completed, the reaction product was transferred to a polycondensation reactor equipped with a stirrer, a cooling condenser and a vacuum system.

An antimony catalyst (Sb, Sigma-Aldrich Co.) was added to the esterification reaction product obtained so as to have a content of 500 ppm or less based on the amount of the antimony element, and triethyl phosphate (TEP) ppm. &lt; / RTI &gt; After the internal temperature of the reactor was raised from 240 ° C to 285 ° C, the pressure was reduced from normal pressure to 50 mmHg for 40 minutes under low vacuum. Ethylene glycol was withdrawn and the pressure was gradually reduced to 0.1 mmHg. The reaction was carried out until viscosity reached. The resultant reactant was discharged and cut into chips to produce a copolymer polyester resin for a calendar.

Example  2 to 4, Comparative Example  1 to 4, 6 and 7: For calendering  Production of polyester resin

A copolymerized polyester resin was prepared using the components and contents shown in Table 1 below.

Comparative Example  5: For calendering  Production of polyester resin

A copolymerized polyester resin was prepared using the components and contents shown in Table 1 below.

In addition, during the polycondensation reaction, methyl methacrylate was added in an amount of 5% by weight based on the amount of the final polymer.

Evaluation example  1: Resin Intrinsic viscosity (IV)

The resin prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was dissolved in Ortho-Chlorophenol at 100 ° C, and then the sample was dropped with an Ostwald viscometer at 35 ° C in a thermostatic chamber And the intrinsic viscosity (IV) was measured.

Evaluation example  2: Calendar processability

The calendering processability of the resins prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was evaluated through the thickness uniformity of the sheet. In this case, when the thickness uniformity is not more than ± 5%, "⊚", when the thickness uniformity is more than ± 5 and less than 10%, when the thickness uniformity is more than ± 10 and less than 15% Quot; X ".

Evaluation example  3: Crystallization heat quantity (? Hc )

The crystallization heat amount (? Hc) of the resins prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was measured by DSC. The polyester resin thus prepared was annealed at 300 for 5 minutes, cooled to room temperature, and then resampled at a heating rate of 0.1 / min to calculate the inherent crystallization calories of the resin.

Evaluation example  4: Economy

The economical efficiency of the resin prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was decreased to more than 5% and less than 7.5% when the manufacturing cost of the conventional alicyclic polyester resin was decreased by more than 7.5 to less than 10% , &Quot;? &Quot;, when it was more than 2.5 to less than 5, it was evaluated as "? &

Room 1 Room 2 Room 3 Room 4 Rain 1 Rain 2 Rain 3 Rain 4 Rain 5 Rain 6 Rain 7 Diacid TPA 100 100 100 100 100 100 100 100 100 100 100 Diol NPG 33 43 57 82 18 - 65 32 35 30 51 EG 67 57 43 18 77 70 35 58 65 70 49 DEG - - - - 5 - - - - - - CHDM - - - - - 30 - 10 - - - Methyl methacrylate - - - - - - - - 5 - - The IV (dl / g) 0.78 0.78 0.72 0.71 0.68 0.75 0.65 0.76 0.75 0.81 0.58 Process index 1.11 1.21 1.29 1.53 0.91 1.05 1.30 1.18 1.10 1.11 1.09 Calendar processability ○ ◎ ◎ ○ X ○ △ ○ △ △ X The crystallization heat amount (? Hc) 2.2 1.5 0.9 0.7 5 0.3 0.5 1.0 1.9 2.4 1.1 Economics ◎ ◎ ◎ ○ ◎ X ○ △ △ ◎ ◎

* Room: Example

* Ratio: Comparative Example

In other words, it was confirmed that Examples 1 to 4 are superior in calendar workability, lower in crystallization heat, and economical in terms of cost, as compared with Comparative Examples 1 to 7.

Claims (14)

1. A calendering polyester resin comprising a dicarboxylic acid repeating unit and a diol repeating unit,
Wherein the dicarboxylic acid repeating unit comprises a terephthalic acid residue,
Wherein the diol repeat unit comprises from 43 to 67 mole percent of ethylene glycol residues and from greater than 30 to less than 57 mole percent of neopentyl glycol residues, based on the total moles of the diol repeat units,
Wherein the diol repeat unit does not comprise an alicyclic diol residue,
Wherein the polyester resin has an intrinsic viscosity (IV) of 0.68 to 3.0 dl / g,
The polyester resin has a haze of 8% or less,
Wherein the polyester resin has a process index of 1.05 to 1.35, defined by the following formula:
<Formula 1>
Process index = {(mol% of diol residue other than ethylene glycol based on the total moles of diol repeating units) / 100} + intrinsic viscosity (dl / g) of polyester resin. The method according to claim 1,
Wherein the dicarboxylic acid repeating unit comprises residues of isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, or a combination thereof. The method according to claim 1,
Wherein the diol repeat unit further comprises diethylene glycol. The method according to claim 1,
Wherein the dicarboxylic acid repeating unit comprises a terephthalic acid residue,
Wherein the diol repeat unit consists of (i) neopentyl glycol residues and (ii) residues of ethylene glycol, diethylene glycol, or combinations thereof. The method according to claim 1,
Wherein the process index of the polyester resin is 1.11 to 1.29. Mixing the mixture so that the molar ratio of the dicarboxylic acid component and the diol component is 1: 1.05 to 1: 3.0, and performing the esterification reaction; And
And polycondensation of the esterified product, the method comprising the steps of:
Wherein the dicarboxylic acid component comprises terephthalic acid,
Wherein the diol component comprises 43 to 67 mole percent ethylene glycol and greater than 30 and less than 57 mole percent neopentyl glycol, based on the total moles of the diol component,
Wherein the diol component does not comprise an alicyclic diol,
Wherein the polyester resin has an intrinsic viscosity (IV) of 0.68 to 3.0 dl / g,
Wherein the polyester resin has a process index of 1.05 to 1.35, defined by the following formula 1:
<Formula 1>
Process index = {(mol% of diol residue other than ethylene glycol based on the total moles of diol repeating units) / 100} + intrinsic viscosity (dl / g) of polyester resin. The method according to claim 6,
Wherein the dicarboxylic acid component comprises isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, or a combination thereof. The method according to claim 6,
Wherein the diol component further comprises diethylene glycol. The method according to claim 6,
Wherein the polycondensation step is carried out at a temperature of 230 to 270 DEG C and a pressure of 0.1 to 3.0 kg / cm &lt; ² &gt;. The method according to claim 6,
Wherein the polycondensation step is carried out in the presence of a polycondensation catalyst and a stabilizer. 11. The method of claim 10,
Wherein the polycondensation catalyst comprises an alkali metal, an alkaline earth metal, antimony, titanium, manganese, cobalt, cerium, germanium or a combination thereof. 11. The method of claim 10,
Wherein the polycondensation catalyst is present in an amount of 50 to 1,000 ppm based on the total weight of the polyester resin. 11. The method of claim 10,
Wherein the stabilizer comprises a phosphorus stabilizer. 11. The method of claim 10,
Wherein the stabilizer is present in an amount of 3,000 ppm or less based on the total weight of the polyester resin.