Heat-shrinkable polyester film and manufacturing method therefor

Abstract

The present invention relates to a heat-shrinkable polyester film and a manufacturing method therefor, wherein the polyester film has excellent heat resistance, transparency, etc. and has crystallinity required in molding processes and / or recycling processes, thereby exhibiting improved moldability and recyclability.

Description

Heat-shrinkable polyester film and method for producing the same

[0001] The present invention relates to a polyester film having excellent heat resistance and recyclability while ensuring heat shrinkage, and a method for producing the polyester film.

[0002] As environmental issues become increasingly serious, technologies for recycling indiscriminately discarded plastic containers (e.g., waste PET bottles) are gaining attention. The recycling process for these waste plastic containers can be divided into physical recycling, which involves washing and crushing, and chemical recycling, which involves depolymerization.

[0003] However, the recyclability of waste plastic containers is reduced due to the packaging materials and / or labels incorporated into the waste plastic containers. Specifically, heat-shrinkable polyester films are incorporated into plastic containers as packaging materials and / or labels. However, due to the difference in crystallinity between the polyester film and the plastic container, recycling of waste plastic containers requires separating (removing) the polyester film from the waste plastic container, which reduces the recyclability of the waste plastic containers. Furthermore, the polyester film used in the heat-shrinking process is manufactured to have low crystallinity by blending a soft component into the polyester resin, making it difficult to improve recyclability, which has been highlighted due to the waste plastic problem.

[0004] Meanwhile, the above recycling process includes a cleaning process in which the polyester film is washed in high-temperature water. When a polyester film is put into the cleaning process, there is also a problem in that it is difficult to determine whether the polyester film has been removed because the increase in haze according to temperature is minimal.

[0005] In addition, conventionally, polymer films (e.g., polyethylene films or polypropylene films) having a density that floats on water were applied as packaging materials and / or labels, so that the flakes of the polymer films were washed and sorted in the washing process. However, since these are not the same material as plastic containers made mostly of PET material, but different materials, if they are not properly washed and sorted and mixed into the recycling process of plastic containers, they act as a source of contamination (impurities), which also reduces recyclability.

[0006] Therefore, there is a need for a polymer film that is made of the same material as a plastic container made of PET material but can be easily removed during the cleaning process.

[0007] In order to solve the above-mentioned conventional problems, the inventors of the present invention have conducted various studies, and as a result, they have confirmed that a polyester film can be obtained that has optimized crystallinity by controlling the change in haze at a specific temperature, thereby exhibiting properties required in the field of heat-shrinkable films (e.g., heat-shrinkability, heat resistance, transparency, processability, etc.) and improving the recyclability of plastic containers.

[0008] Accordingly, the object of the present invention is to provide a polyester film with controlled haze changes at a specific temperature and a method for producing the same. Specifically, the object of the present invention is to provide a polyester film and a method for producing the same, which increases haze at a specific temperature, enabling easy removal during the washing and sorting process of flakes (e.g., flakes obtained by crushing PET bottles to which polyester films are bonded), thereby improving recyclability.

[0009] In order to solve the above problem, the present invention comprises a polyester resin including a diol repeating unit derived from a diol component; and a dicarboxylic acid repeating unit derived from a dicarboxylic acid component, and has a heat shrinkage rate in the main shrinkage direction of 50% or more at 85°C, and when T1 is 80°C and T2 is 85°C, an average haze change rate (ΔH) according to the following formula 1 ave ) provides a polyester film having a thickness of 0.5 to 10:

[0010] [Formula 1]

[0011] ΔH ave (% / ℃) = │H T2 - H T1 │ / │T2 - T1│

[0012] In the above equation 1,

[0013] H T1 is the haze (%) of the polyester film at the T1 temperature,

[0014] H T2 is the haze (%) of the polyester film at temperature T2.

[0015] In addition, the present invention comprises (1) a step of manufacturing a polyester resin by polymerizing a diol component and a dicarboxylic acid component; (2) a step of manufacturing a stretched film from the polyester resin; and (3) a step of heat-setting the stretched film, wherein the heat shrinkage in the main shrinkage direction at 85°C is 50% or more, and when T1 is 80°C and T2 is 85°C, the average haze change rate (ΔH) according to the above formula 1 ave ) provides a method for manufacturing a polyester film having a thickness of 0.5 to 10.

[0016] The polyester film according to the present invention can have high crystallinity by controlling the change in haze at a specific temperature. In particular, when the polyester film according to the present invention is crushed together with waste plastic containers to form mixed flakes and then washed and sorted, the haze increases at a specific temperature (e.g., the temperature of the water used for washing) and takes on an opaque color, so that the film can be easily removed (sorted) during the washing and sorting process.

[0017] Therefore, the present invention can increase the recyclability of waste plastic containers by enabling the recycling process of waste plastic containers to which the polyester film is combined without performing the task of separating (removing) the polyester film. In addition, the polyester film according to the present invention can be usefully applied as a heat-shrinkable film for forming packaging materials and / or labels for plastic containers due to its excellent heat-shrinkability, heat resistance, transparency, and processability.

[0018] Hereinafter, the present invention will be described in detail. Herein, the present invention is not limited to the contents described below, and may be modified in various forms as long as the gist of the invention is not changed.

[0019] The word "comprising" or "including" in this specification is intended to specify particular 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.

[0020] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification can be understood to be modified by the term “about” in all cases unless otherwise specified.

[0021]

[0022] The present invention relates to a polyester film and a method for manufacturing the same, which can control a change in haze at a specific temperature within a desired range by controlling the content of a specific component, controlling a stretching / shrinking process, etc., thereby exhibiting high crystallinity and excellent heat shrinkage properties, and which will be described in detail as follows.

[0023]

[0024] polyester film

[0025] A polyester film according to the present invention comprises a polyester resin including a diol repeating unit derived from a diol component; and a dicarboxylic acid repeating unit derived from a dicarboxylic acid component, and has a heat shrinkage rate in the main shrinkage direction of 50% or more at 85°C, and when T1 is 80°C and T2 is 85°C, the average haze change rate (ΔH) according to the following formula 1 ave ) represents 0.5 to 10.

[0026] [Formula 1]

[0027] ΔH ave (% / ℃) = │H T2 - H T1 │ / │T2 - T1│

[0028] In the above equation 1,

[0029] H T1 is the haze of the polyester film at the T1 temperature,

[0030] H T2 is the haze of the polyester film at temperature T2.

[0031] The above main shrinkage direction may be longitudinal (MD) or transverse (TD), and preferably transverse (TD).

[0032] Specifically, the polyester film may have a heat shrinkage ratio in the main shrinkage direction at 85°C of 51% or more, 52% or more, 53% or more, 54% or more, 55% or more, 56% or more, 57% or more, 58% or more, 59% or more, or 60% or more (e.g., 50 to 60%, 50 to 58%, 51 to 58%, 51 to 57%, or 52 to 56%).

[0033] According to the present invention, the polyester film may have a heat shrinkage rate in the main shrinkage direction of 60% or more at 90°C, specifically, 61% or more, 63% or more, 64% or more, 66% or more, 68% or more, 70% or more, 72% or more, 74% or more, 76% or more, 78% or more, or 80% or more (e.g., 60 to 80%, 62 to 79%, 64 to 79%, 65 to 78%, or 66 to 78%).

[0034] Since the heat shrinkage rates in the main shrinkage direction at 85°C and 90°C are within the above ranges, the heat shrinkability of the polyester film is excellent, and thus the polyester film can be usefully applied as a heat shrinkable film for forming packaging materials and / or labels. The main shrinkage direction may be the transverse direction (TD) or the longitudinal direction (MD).

[0035] Meanwhile, the polyester film has an average haze change rate (ΔH) according to the above formula 1 when the above T1 is 80°C and the above T2 is 85°C. ave) is 0.5 to 10, and specifically, 0.6 to 10, 0.7 to 10, 0.8 to 10, 0.9 to 10, 1 to 10, 1.3 to 9.9, 1.5 to 9.8, 1.8 to 9.7, 2.0 to 9.6, 2.3 to 9.5, 2.6 to 9.4, 3.0 to 9.3, 3.5 to 9.2, 4.0 to 9.1, or 5.0 to 9.0. When the T1 is 80 ℃ and the T2 is 85 ℃, the haze average change rate (ΔH) according to the above formula 1 ave ) is less than 0.5, it means that the polyester film does not have the crystallinity required in the washing process and recycling process, so the recyclability of the polyester film may be significantly reduced. Conversely, the average haze change rate (ΔH) according to the above equation 1 ave ) exceeds 10, it means that the crystallinity of the polyester film is excessively high and the transparency is low, so it may be difficult to secure the formability and transparency of the polyester film.

[0036] According to the present invention, the polyester film has an average haze change rate (ΔH) according to the above formula 1 when the above T1 is 85°C and the above T2 is 90°C. ave ) may be 1 to 5, and specifically 1.3 to 4.9, 1.5 to 4.9, 1.8 to 4.8, 2.0 to 4.8, 2.2 to 4.7, 2.4 to 4.7, 2.5 to 4.6, 2.7 to 4.5, 2.9 to 4.5, or 3.0 to 4.4.

[0037] In addition, according to the present invention, the polyester film has an average haze change rate (ΔH) according to the above formula 1 when the above T1 is 75°C and the above T2 is 80°C. ave) may be 0.5 to 8, and specifically 0.8 to 7.5, 1.0 to 7.3, 1.3 to 7.0, 1.5 to 6.8, 1.6 to 6.5, 1.7 to 6.3, 1.8 to 6.0, 2.0 to 5.8, 2.5 to 5.5, or 3.0 to 5.0.

[0038] In this way, the haze change at relatively high temperatures of 75 ℃, 80 ℃, 85 ℃ and 90 ℃ is expressed as the average haze change rate (ΔH ave ) is defined as the average haze change rate (ΔH) at each specific temperature. ave ) is controlled within the above range, the polyester film has high crystallinity while ensuring formability and transparency, so the present invention can provide a polyester film with excellent recyclability, formability and transparency. Meanwhile, the average haze change rate (ΔH ave ) can be expressed as % / ℃.

[0039] According to the present invention, the polyester film may have a haze of 10% or more at 80°C and a haze of 50% or more at 90°C. Specifically, the polyester film may have a haze of 11% or more, 13% or more, 15% or more, 17% or more, 20% or more, 22% or more, 24% or more, 26% or more, 28% or more, 30% or more, 32% or more, 34% or more, or 35% or more (e.g., 10 to 35%, 15 to 34%, 20 to 33%, 23 to 32%, 25 to 31%, or 27 to 30%) at 80°C. Additionally, the polyester film may have a haze at 90°C of 53% or more, 56% or more, 60% or more, 63% or more, 65% or more, 68% or more, 70% or more, 73% or more, 75% or more, 78% or more, 80% or more, 82% or more, or 86% or more (e.g., 50 to 90%, 55 to 86%, 60 to 84%, 65 to 83%, 70 to 82%, or 72 to 80%).

[0040] In addition, according to the present invention, the polyester film has a haze (H) at 80°C 80 ) and haze (H) at 75 ℃ 75 ) of the car (H) 80 - H 75 ) is 7 to 30%, and the haze (H) at 85 ℃ 85 ) and haze (H) at 80 ℃ 80 ) of the car (H) 85 - H 80 ) is 10 to 50%, and the haze (H) at 90 ℃ 90 ) and haze at 85 ℃ (H 85 ) of the car (H) 90 - H 85 ) may be 10 to 25%. Specifically, the above difference (H 80 - H 75) may be 7.3 to 29.5%, 7.5 to 29.5%, 8 to 29%, 8.5 to 29%, 9 to 28.5%, 10 to 28.5%, 15 to 28%, 20 to 28%, or 20.5 to 27.5%. In addition, the difference (H 85 - H 80 ) may be 10.5 to 49%, 11.5 to 48.5%, 15 to 48%, 20 to 47.5%, 25 to 47%, 28 to 46.5%, 30 to 45%, 32 to 43%, or 33 to 40%. In addition, the difference (H 90 - H 85 ) may be 12 to 24.5%, 13 to 24%, 14 to 23.5%, 15 to 23%, 16 to 22.5%, 16.5 to 22%, 17 to 21.5%, 17.3 to 21%, or 18 to 20.5%.

[0041] Each haze at 80 ℃ and 90 ℃ and the difference in haze according to temperature (H 80 - H 75 , H 85 - H 80 , H 90 - H 85 ) are each controlled within the above range, the polyester film of the present invention can have excellent recyclability, heat resistance, formability, and transparency.

[0042] The polyester film according to the present invention has the contents of metal components and non-metal components controlled within specific ranges, and as a result, the haze increase rate of the polyester film according to temperature is large, which leads to an increase in the crystallinity of the polyester film, thereby enhancing the recyclability of the polyester film.

[0043] For example, according to the present invention, the polyester film may have a metal content of 5 to 250 ppm as measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Specifically, the metal content may be 8 to 240 ppm, 10 to 230 ppm, 13 to 220 ppm, 15 to 200 ppm, 18 to 190 ppm, 20 to 180 ppm, 25 to 175 ppm, 30 to 170 ppm, 35 to 165 ppm, 40 to 160 ppm, 45 to 155 ppm, or 50 to 150 ppm.

[0044] The above metal is derived from raw material components (e.g., catalyst, coloring agent, crystallizer, etc.) input during the production of a polyester film, and acts as a crystal nucleus during the production of a polyester film (or polyester resin), thereby enabling a polyester film with high crystallinity to be obtained. The metal is not particularly limited, but may include at least one selected from the group consisting of antimony (Sb), titanium (Ti), zinc (Zn), germanium (Ge), magnesium (Mg), and manganese (Mn), thereby enabling the polyester film to have the desired crystallinity.

[0045] In addition, according to the present invention, the polyester film may have a phosphorus (P) content of 5 to 200 ppm as measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Specifically, the phosphorus (P) content may be 5 to 198 ppm, 7 to 195 ppm, 9 to 190 ppm, 10 to 185 ppm, 13 to 180 ppm, 15 to 170 ppm, 17 to 160 ppm, 20 to 150 ppm, 22 to 130 ppm, 25 to 120 ppm, 26 to 100 ppm, 27 to 50 ppm, or 27 to 28 ppm.

[0046] Meanwhile, the polyester film may have a total content of metal and phosphorus (P) (metal content + phosphorus (P) content) of 10 to 450 ppm as measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and specifically, may be 20 to 400 ppm, 30 to 350 ppm, 40 to 330 ppm, 50 to 300 ppm, 60 to 280 ppm, 65 to 275 ppm, 80 to 270 ppm, or 90 to 265 ppm.

[0047] According to the present invention, the polyester film has a melting temperature (T m ) may be 230 ℃ or less, and specifically, 225 ℃ or less, 220 ℃ or less, 215 ℃ or less, 210 ℃ or less, 205 ℃ or less, 200 ℃ or less, 195 ℃ or less, 185 ℃ or less, 175 ℃ or less, 165 ℃ or less, 155 ℃ or less, or 150 ℃ or less (e.g., 150 to 230 ℃, 151 to 220 ℃, 152 to 210 ℃, 153 to 200 ℃, 154 to 195 ℃, or 155 to 180 ℃). The melting temperature (T m ) can provide a polyester film having excellent formability (processability) while having the desired crystallinity within the above range.

[0048] Meanwhile, the polyester film includes a diol repeating unit derived from a diol component; and a dicarboxylic acid repeating unit derived from a dicarboxylic acid component.

[0049] According to the present invention, the diol component for forming the diol repeating unit may not be particularly limited as long as it is a commonly known diol component. Specifically, the diol component may be bis-2-hydroxyethyl terephthalate, isosorbide, neopentyl glycol, ethylene glycol, diethylene glycol, cyclohexanedimethanol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, It may include at least one (e.g., at least two, at least three, at least four, or at least five) selected from the group consisting of 4-(hydroxymethyl)cyclohexylmethyl-4-(hydroxymethyl)cyclohexanecarboxylate (CHDM derivative), 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol (CHDM derivative), recycled bis-2-hydroxyethyl terephthalate, recycled isosorbide, recycled neopentyl glycol, recycled ethylene glycol, recycled diethylene glycol, and recycled cyclohexanedimethanol.

[0050] More specifically, the diol component may include at least one selected from the group consisting of a first diol component comprising ethylene glycol (EG), recycled ethylene glycol (r-EG), or a combination thereof; a second diol component comprising bis-2-hydroxyethyl terephthalate (BHET), recycled bis-2-hydroxyethyl terephthalate (r-BHET), or a combination thereof; and a third diol component comprising isosorbide (ISB), diethylene glycol (DEG), cyclohexanedimethanol (CHDM), neopentyl glycol (NPG), recycled isosorbide (r-ISB), recycled diethylene glycol (r-DEG), recycled cyclohexanedimethanol (r-CHDM), recycled neopentyl glycol (r-NPG), or a combination thereof.

[0051] The amount of the first diol component used (amount added during reaction) is not particularly limited, but may be 50 to 95 mol%, 55 to 95 mol%, 60 to 93 mol%, 65 to 93 mol%, 70 to 90 mol%, 75 to 90 mol%, or 80 to 85 mol% based on the total mol% of the diol component. Accordingly, the polyester resin may include a repeating unit (a) derived from the first diol component. When the amount of the first diol component used is within the above range, a polyester resin having excellent basic physical properties can be economically manufactured.

[0052] The amount of the second diol component used (amount added during reaction) is not particularly limited, but may be 5 to 90 mol%, 5.5 to 80 mol%, 6 to 70 mol%, 7 to 60 mol%, 8 to 50 mol%, 9 to 40 mol%, or 10 to 30 mol%, based on the total mol% of the diol component. Accordingly, the polyester resin may include a repeating unit (b) derived from the second diol component. When the amount of the second diol component used is within the above range, a polyester resin having a viscosity at a level required in a film manufacturing process can be manufactured, thereby providing a polyester film having excellent quality.

[0053] The amount of the third diol component used (amount added during reaction) is not particularly limited, but may be 1 to 45 mol%, 2 to 43 mol%, 3 to 40 mol%, 4 to 40 mol%, 5 to 40 mol%, 6 to 40 mol%, or 7 to 40 mol%, based on the total mol% of the diol component. Accordingly, the polyester resin may include a repeating unit (c) derived from the third diol component. When the amount of the third diol component used is within the above range, a polyester resin having excellent moldability (processability) in addition to basic physical properties can be manufactured.

[0054] For example, when considering the basic physical properties and moldability (processability) of the polyester resin, the amount of isosorbide or regenerated isosorbide among the third diol components may be 0 to 5 mol%, 0.1 to 4 mol%, 0.3 to 3 mol%, or 0.5 to 2 mol%, based on the total mol% of the diol components. In addition, the amount of diethylene glycol or regenerated diethylene glycol among the third diol components may be 5 to 30 mol%, 6 to 28 mol%, 7 to 26 mol%, or 8 to 25 mol%, based on the total mol% of the diol components. In addition, the amount of cyclohexanedimethanol or recycled cyclohexanedimethanol among the third diol components may be 0 to 35 mol%, 3 to 33 mol%, 5 to 30 mol%, or 10 to 28 mol%, based on the total mol% of the diol components. In addition, the amount of neopentyl glycol or recycled neopentyl glycol among the third diol components may be 0 to 20 mol%, 1 to 18 mol%, 1.5 to 16 mol%, or 2 to 10 mol%, based on the total mol% of the diol components.

[0055] According to the present invention, the dicarboxylic acid component for forming the dicarboxylic acid repeating unit may not be particularly limited as long as it is a commonly known dicarboxylic acid component. Specifically, the dicarboxylic acid component may include at least one selected from the group consisting of terephthalic acid, isophthalic acid, dimethyl phthalate, dimethyl isophthalate, dimethyl terephthalate, phthalic acid, phthalic anhydride, 2,6-naphthalene dicarboxylic acid, dimethyl 2,6-naphthalene dicarboxylate, diphenyl dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, dimethyl 1,4-cyclohexane dicarboxylate, dimethyl 1,3-cyclohexane dicarboxylate, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, glutaric acid, azelaic acid, and regenerated terephthalic acid.

[0056] Meanwhile, the recycled bis-2-hydroxyethyl terephthalate, the recycled isosorbide, the recycled neopentyl glycol, the recycled ethylene glycol, the recycled diethylene glycol, the recycled cyclohexanedimethanol and the recycled terephthalic acid may refer to recycled raw materials (monomers) obtained by subjecting used waste polyester resin or waste polyester articles (e.g., films, sheets, fibers, containers, etc.) to a commonly known depolymerization process.

[0057] The polyester resin comprising the above diol repeating unit and the above dicarboxylic acid repeating unit may have an intrinsic viscosity (IV) (@35°C) of 0.5 to 0.9 dl / g. Specifically, the polyester resin may have an intrinsic viscosity (IV) of 0.5 to 0.87 dl / g, 0.5 to 0.85 dl / g, 0.55 to 0.83 dl / g, 0.58 to 0.82 dl / g, 0.6 to 0.81 dl / g, or 0.63 to 0.80 dl / g at 35°C.

[0058] The above polyester resin may be in the form of chips, pellets, or powder.

[0059] These polyester resins may be homopolymers or copolymers. Specifically, the polyester resins may 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).

[0060]

[0061] Method for manufacturing polyester film

[0062] The method for manufacturing a polyester film according to the present invention comprises the steps of (1) manufacturing a polyester resin by polymerizing a diol component and a dicarboxylic acid component; (2) manufacturing a stretched film from the polyester resin; and (3) heat-setting the stretched film. The polyester film manufactured through the above steps has a heat shrinkage rate in the main shrinkage direction of 50% or more at 85°C, and when T1 is 80°C and T2 is 85°C, the average haze change rate (ΔH) according to the following equation 1 ave ) is 0.5 to 10. A specific description of the manufacturing method of such polyester film is as follows. Here, a specific description of the following formula 1 is omitted because it is the same as described above.

[0063] [Formula 1]

[0064] ΔH ave (% / ℃) = │H T2 - H T1 │ / │T2 - T1│

[0065] In the above equation 1,

[0066] H T1 is the haze of the polyester film at the T1 temperature,

[0067] H T2 is the haze of the polyester film at temperature T2.

[0068]

[0069] Step (1): Preparation of polyester resin

[0070] The above step (1) is a step for manufacturing a polyester resin by subjecting a diol component and a dicarboxylic acid component to an esterification reaction (or ester exchange reaction) to obtain a reactant (e.g., an oligomer), and then subjecting the reactant to a condensation polymerization reaction. Here, a specific description of the diol component and the dicarboxylic acid component is omitted as it is the same as described above.

[0071] The conditions under which the esterification reaction (or ester exchange reaction) is performed may not be particularly limited. Specifically, the temperature at which the esterification reaction is performed may be 230 to 290°C, 235 to 285°C, 240 to 280°C, 245 to 275°C, or 250 to 275°C. In addition, the pressure at which the esterification reaction is performed may be 0 to 4 kgf / cm2, 0.5 to 3.5 kgf / cm2, 0.5 to 3 kgf / cm2, 1 to 2.5 kgf / cm2, or 1 to 2 kgf / cm2. As the esterification reaction is performed under the above conditions, a reactant (oligomer) having a desired molecular weight can be obtained in high yield while minimizing the production of side products.

[0072] In the reactor where the above esterification reaction (or ester exchange reaction) takes place, one or more additives selected from the group consisting of a catalyst, a coloring agent, a crystallizer, an antioxidant, and a branching agent may be added together with the above diol component and the above dicarboxylic acid component.

[0073] As the catalyst, sodium or magnesium methylate; acetate, borate, fatty acid salt, or carbonate of Ge, Zn, Cd, Mn, Co, Ca, Ba, etc.; or oxides or hydrates of Ge, Mg, Pb, Mn, Ti, Sb, Sn, Al, etc. can be used. For example, as the catalyst, tetraethyl titanate, acetyltripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, octylene glycol titanate, triethanolamine titanate, acetylacetonate titanate, ethylacetoacetic ester titanate, isostearyl titanate, titanium dioxide, germanium dioxide, germanium tetrachloride, germanium ethylene glycoside, germanium acetate, or a combination thereof can be used.

[0074] As the above coloring agent, organic compounds such as cobalt compounds, anthraquionone compounds, perinone compounds, azo compounds, and methine compounds (e.g., cobalt acetate, cobalt propionate, Clarient's Polysynthren Blue RLS toner, Clarient's Solvaperm Red BB toner) can be used.

[0075] As the above crystallizing agent, a crystal nucleating agent, an ultraviolet absorber, a polyolefin resin, a polyamide resin, etc. can be used.

[0076] As the above antioxidant, hindered phenol compounds, phosphite compounds, thioether compounds, etc. can be used.

[0077] As the branching agent, trimellitic acid, trimellitic anhydride, trimethylol propane, or a combination thereof may be used.

[0078] The reactants obtained through the above esterification reaction (or ester exchange reaction) may then be introduced into a polycondensation reactor to carry out a polycondensation reaction. The conditions under which the polycondensation reaction is performed may not be particularly limited. Specifically, the temperature at which the polycondensation reaction is performed may be 250 to 300°C, 255 to 295°C, 260 to 290°C, 265 to 285°C, or 270 to 285°C. In addition, the pressure at which the polycondensation reaction is performed may be a pressure (reduced pressure) lower than atmospheric pressure (e.g., 1 atm). As the polycondensation reaction is performed under the above conditions, a polyester resin (polymer) with excellent processability can be efficiently produced.

[0079] Thereafter, the polyester resin obtained through the above-described polycondensation reaction can undergo a pelletizing process including processes such as extrusion and underwater cutting.

[0080]

[0081] Step (2): Manufacturing of stretch film

[0082] The above step (2) is a step for manufacturing a stretched film from the polyester resin obtained in the above step (1). Specifically, the stretched film can be manufactured by extruding the polyester resin to manufacture an unstretched sheet and then stretching it.

[0083] The extrusion of the above polyester resin can be performed by a conventionally known method, and at this time, the extrusion temperature can be specifically 230 to 300°C, 240 to 290°C, 250 to 280°C, or 260 to 270°C.

[0084] The unstretched sheet obtained through the above extrusion may undergo a preheating process before undergoing the stretching process. The preheating of the unstretched sheet is performed to lower the glass transition temperature (T) of the polyester resin. g ) as a basis, T g +5℃ to T g It can be performed at +50℃, and specifically, at 70 to 100℃. As preheating is performed within the above range, the unstretched sheet has flexibility suitable for the stretching process, thereby minimizing breakage of the unstretched sheet during the stretching process.

[0085] The stretching of the above-mentioned unstretched sheet may be uniaxial stretching in either the longitudinal direction (MD) or the transverse direction (TD), or biaxial stretching in both the longitudinal direction (MD) and the transverse direction (TD).

[0086] When the above-mentioned unstretched sheet is stretched in the machine direction (MD), the stretching ratio is not particularly limited, but considering the crystallinity of the polyester resin, it may be 1.5 to 6 times, 1.7 to 5.8 times, 1.8 to 5.5 times, 2 to 5.3 times, or 2.5 to 5 times. In addition, when the above-mentioned unstretched sheet is stretched in the transverse direction (TD), the stretching ratio is not particularly limited, but considering the crystallinity of the polyester resin, it may be 1.1 to 5 times, 1.3 to 5 times, 1.5 to 5 times, 2 to 5 times, or 3 to 5 times.

[0087] Meanwhile, the stretching temperature of the above unstretched sheet is not particularly limited, but the glass transition temperature (T) of the polyester resin g ) based on T g +5℃ to T g +20℃, or T g +8℃ to T g It can be +10℃, and specifically, it can be 55 to 180℃, 60 to 170℃, 63 to 150℃, 65 to 130℃, 68 to 110℃, 70 to 100℃, or 70 to 95℃. As the stretching temperature is within the above range, a polyester film with a controlled haze change as desired can be manufactured.

[0088]

[0089] Step (3): Open and close

[0090] The above step (3) is a step of heat-setting the stretched film obtained in the above step (2). The heat-setting temperature of the stretched film is not particularly limited, but is the glass transition temperature (T) of the polyester resin. g ) based on T g +5℃ to T gIt may be +50°C, and specifically 60 to 200°C, 65 to 190°C, 70 to 180°C, 75 to 170°C, 80 to 165°C, 85 to 160°C, or 90 to 130°C.

[0091] The present invention is described in more detail through the following examples. However, the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention.

[0092]

[0093] <Manufacturing of polyester resin>

[0094] [Example 1]

[0095] Into a 10 L reactor connected to a column and a water-cooled condenser, regenerated bis-2-hydroxyethyl terephthalate (r-BHET, 588.6 g), terephthalic acid (TPA, 3461.9 g), isosorbide (ISB, 48.3 g), ethylene glycol (EG, 1148.5 g), 1,4-cyclohexanedimethanol (CHDM, 778.6 g), regenerated diethylene glycol (r-DEG, 375.7 g), Ge catalyst (5.0 g), Ti catalyst (1.5 g), phosphoric acid (0.6 g), blue toner (0.005 g), and red toner (0.003 g) were charged. Next, the temperature of the reactor was raised to 265 ℃, and an esterification reaction (ES) was performed at 265 ℃ under a pressure of 2 kgf / ㎠ to obtain a transparent reactant.

[0096] Next, the reactants were transferred to a polycondensation reactor, and a polycondensation reaction (PA) was performed at 270°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (melt intrinsic viscosity) (IV) of the reactants inside the polycondensation reactor reached 0.77 dl / g, the reactants were discharged outside the polycondensation reactor and stranded. Subsequently, the reactants were solidified with a cooling liquid, and then granulated to an average weight of approximately 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0097]

[0098] [Example 2]

[0099] Into a 10 L reactor connected to a column and a water-cooled condenser were charged regenerated bis-2-hydroxyethyl terephthalate (r-BHET, 3517.7 g), terephthalic acid (TPA, 1532.6 g), regenerated ethylene glycol (r-EG, 22.8 g), 1,4-cyclohexanedimethanol (CHDM, 627.8 g), neopentyl glycol (NPG, 53.3 g), diethylene glycol (DEG, 374.2 g), cyclohexanedimethanol derivative (CHDM derivative, 123.7 g), Ti catalyst (0.4 g), phosphoric acid (0.4 g), blue toner (0.005 g), and red toner (0.005 g). Next, the temperature of the reactor was raised to 255 ℃, and an esterification reaction (ES) was performed at 255 ℃ under a pressure of 1 kgf / ㎠ to obtain a transparent reactant.

[0100] Next, the reactants were transferred to a polycondensation reactor, and a polycondensation reaction (PA) was performed at 285°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (melt intrinsic viscosity) (IV) of the reactants inside the polycondensation reactor reached 0.65 dl / g, the reactants were discharged outside the polycondensation reactor and stranded. Subsequently, the reactants were solidified with a cooling liquid, and then granulated to an average weight of approximately 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0101]

[0102] [Example 3]

[0103] In a 10 L reactor connected to a column and a water-cooled condenser, regenerated bis-2-hydroxyethyl terephthalate (r-BHET, 1756.6 g), terephthalic acid (TPA, 2678.7 g), ethylene glycol (EG, 721.2 g), regenerated 1,4-cyclohexanedimethanol (r-CHDM, 922.1 g), diethylene glycol (DEG, 287.5 g), Ti catalyst (0.2 g), phosphoric acid (3.5 g), blue toner (0.005 g), and red toner (0.005 g) were charged. Next, the temperature of the reactor was raised to 273 ℃, and an esterification reaction (ES) was performed at 273 ℃ under a pressure of 0 kgf / cm2 to obtain a transparent reactant.

[0104] Next, the reactants were transferred to a polycondensation reactor, and a polycondensation reaction (PA) was performed at 275°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (melt intrinsic viscosity) (IV) of the reactants inside the polycondensation reactor reached 0.80 dl / g, the reactants were discharged outside the polycondensation reactor and stranded. Subsequently, the reactants were solidified with a cooling liquid, and then granulated to an average weight of approximately 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0105]

[0106] [Example 4]

[0107] A 10 L reactor equipped with a column and a water-cooled condenser was charged with regenerated bis-2-hydroxyethyl terephthalate (r-BHET, 4240.6 g), terephthalic acid (TPA, 1187.8 g), ethylene glycol (EG, 117.9 g), 1,4-cyclohexanedimethanol (CHDM, 534.2 g), diethylene glycol (DEG, 416.4 g), a Ge catalyst (1.0 g), a Ti catalyst (0.1 g), phosphoric acid (7.0 g), blue toner (0.025 g), and red toner (0.010 g). Next, the temperature of the reactor was raised to 260 ℃, and an esterification reaction (ES) was performed at 260 ℃ under a pressure of 1 kgf / cm2 to obtain a transparent reactant.

[0108] Next, the reactants were transferred to a polycondensation reactor, and a polycondensation reaction (PA) was performed at 275°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (melt intrinsic viscosity) (IV) of the reactants inside the polycondensation reactor reached 0.78 dl / g, the reactants were discharged outside the polycondensation reactor and stranded. Subsequently, the reactants were solidified with a cooling liquid, and then granulated to an average weight of approximately 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0109]

[0110] [Example 5]

[0111] A 10 L reactor equipped with a column and a water-cooled condenser was charged with regenerated bis-2-hydroxyethyl terephthalate (r-BHET, 1266.8 g), terephthalic acid (TPA, 3311.7 g), ethylene glycol (EG, 1506.7 g), regenerated neopentyl glycol (r-NPG, 432.3 g), diethylene glycol (DEG, 155.5 g), Ge catalyst (5.0 g), Ti catalyst (0.2 g), phosphoric acid (4.0 g), cobalt acetate (0.2 g), blue toner (0.015 g), and red toner (0.005 g). Next, the temperature of the reactor was raised to 250 °C, and an esterification reaction (ES) was performed at 250 °C under a pressure of 1 kgf / cm2 to obtain a transparent reactant.

[0112] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction (PA) was performed at 285°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (melt intrinsic viscosity) (IV) of the reactants inside the polycondensation reactor reached 0.70 dl / g, the reactants were discharged outside the polycondensation reactor and stranded. Subsequently, the reactants were solidified with a cooling liquid, and then granulated to an average weight of approximately 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0113]

[0114] [Comparative Example 1]

[0115] Regenerated bis-2-hydroxyethyl terephthalate (r-BHET, 1254.9 g), terephthalic acid (TPA, 3280.6 g), ethylene glycol (EG, 1577.7 g), 1,4-cyclohexanedimethanol (CHDM, 395.3 g), diethylene glycol (DEG, 154.0 g), Ti catalyst (0.3 g), phosphoric acid (2.0 g), blue toner (0.005 g), and red toner (0.005 g) were charged into a 10 L reactor connected to a column and a water-cooled condenser. Next, the temperature of the reactor was raised to 263 ℃, and an esterification reaction (ES) was performed at 263 ℃ under a pressure of 1 kgf / cm2 to obtain a transparent reactant.

[0116] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction (PA) was performed at 285°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (melt intrinsic viscosity) (IV) of the reactants inside the polycondensation reactor reached 0.70 dl / g, the reactants were discharged outside the polycondensation reactor and stranded. Subsequently, the reactants were solidified with a cooling liquid, and then granulated to an average weight of approximately 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0117]

[0118] [Comparative Example 2]

[0119] Regenerated bis-2-hydroxyethyl terephthalate (r-BHET, 554.1 g), terephthalic acid (TPA, 3259.2 g), ethylene glycol (EG, 1448.9 g), 1,4-cyclohexanedimethanol (CHDM, 349.0 g), diethylene glycol (DEG, 272.0 g), Ti catalyst (2.5 g), phosphoric acid (0.2 g), blue toner (0.010 g), and red toner (0.005 g) were charged into a 10 L reactor connected to a column and a water-cooled condenser. Next, the temperature of the reactor was raised to 263 ℃, and an esterification reaction (ES) was performed at 263 ℃ under a pressure of 0 kgf / cm2 to obtain a transparent reactant.

[0120] Next, the reactants were transferred to a polycondensation reactor, and a polycondensation reaction (PA) was performed at 275°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (melt intrinsic viscosity) (IV) of the reactants inside the polycondensation reactor reached 0.78 dl / g, the reactants were discharged outside the polycondensation reactor and stranded. Subsequently, the reactants were solidified with a cooling liquid, and then granulated to an average weight of approximately 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0121]

[0122] [Comparative Example 3]

[0123] Into a 10 L reactor connected to a column and a water-cooled condenser, terephthalic acid (TPA, 3316.3 g), ethylene glycol (EG, 1237.0 g), 1,4-cyclohexanedimethanol (CHDM, 2237.5 g), diethylene glycol (DEG, 49.8 g), a Ge catalyst (1.0 g), a Ti catalyst (0.5 g), blue toner (0.005 g), and red toner (0.005 g) were charged. Next, the temperature of the reactor was raised to 263 ℃, and an esterification reaction (ES) was performed at 263 ℃ under a pressure of 1 kgf / cm2 to obtain a transparent reactant.

[0124] Next, the reactants were transferred to a polycondensation reactor, and a polycondensation reaction (PA) was performed at 275°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (melt intrinsic viscosity) (IV) of the reactants inside the polycondensation reactor reached 0.70 dl / g, the reactants were discharged outside the polycondensation reactor and stranded. Subsequently, the reactants were solidified with a cooling liquid, and then granulated to an average weight of approximately 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0125]

[0126] <Manufacturing of polyester film>

[0127] [Manufacturing Example 1]

[0128] The polyester resin chips manufactured in Example 1 were fed into an extruder and melt-extruded at a temperature of 250 to 270°C and cast at a temperature of 70 to 90°C to produce an unstretched sheet having a thickness of 250 μm. Then, the unstretched sheet was heated to 78 to 80°C and stretched only in the transverse direction (TD) at a stretch ratio of 5 to produce a stretched film. Thereafter, the stretched film was heat-set to produce a polyester film having a thickness of 40 to 60 μm (average thickness: about 50 μm).

[0129]

[0130] [Manufacturing Examples 2 to 5]

[0131] Instead of the polyester resin chips manufactured in Example 1, the polyester resin chips manufactured in Examples 2 to 5 were applied, respectively, but the stretching temperature of the unstretched sheet was set to T g +8℃ to T g +10℃(T g : A polyester film was manufactured through the same process as Manufacturing Example 1, except that the glass transition temperature of the polyester resin chip was adjusted.

[0132]

[0133] [Comparative Manufacturing Examples 1 to 3]

[0134] Instead of the polyester resin chips manufactured in Example 1, the polyester resin chips manufactured in Comparative Examples 1 to 3 were applied, but the stretching temperature of the unstretched sheet was T g +8℃ to T g +10℃(T g : A polyester film was manufactured through the same process as Manufacturing Example 1, except that the glass transition temperature of the polyester resin chip was adjusted.

[0135]

[0136] [Experimental Example 1] Average Haze Change Rate

[0137] Each of the polyester films (width: 8 cm, length: 3 cm / width (TD), length (MD)) manufactured in Manufacturing Examples 1 to 5 and Comparative Manufacturing Examples 1 to 3 was placed in a water bath containing water at 95°C and shrunk for 15 seconds to form a heat-shrinkable film bonded to a PET bottle. Next, each of the polyester films that underwent the shrinkage and drying process was cut into sizes of 2 cm in width and 2 cm in length to manufacture polyester film specimens, which were placed in water baths containing water at 75°C, 80°C, 85°C, and 90°C, respectively, and kept in an immersed state for 15 minutes. Next, the immersed polyester film specimens were taken out from each water bath and left at room temperature for 30 minutes or more to slowly lower the temperature of the polyester film specimens to room temperature, thereby performing an air cooling process. Next, the haze of polyester film specimens was measured at different temperatures under ASTM D1003 conditions. Then, according to Equation 1 below, the average haze change rate (ΔH) was calculated when T1 was 75 ℃ and T2 was 80 ℃, when T1 was 80 ℃ and T2 was 85 ℃, and when T1 was 85 ℃ and T2 was 90 ℃. ave ) was calculated, and the results are shown in Table 1 below. In addition, the difference in haze (H) of polyester film specimens by temperature 80 - H 75 , H 85 - H 80 , H 90 - H 85 ) was also confirmed.

[0138] [Formula 1]

[0139] ΔH ave (% / ℃) = │H T2 - H T1 │ / │T2 - T1│

[0140] In the above equation 1,

[0141] H T1is the haze of the polyester film at the T1 temperature,

[0142] H T2 is the haze of the polyester film at temperature T2.

[0143]

[0144] [Test Example 2] Heat shrinkage rate

[0145] The heat shrinkage rate of each polyester film manufactured in Manufacturing Examples 1 to 5 and Comparative Manufacturing Examples 1 to 3 was evaluated as follows, and the results are shown in Table 1 below.

[0146] Preparation of specimens: Polyester film was cut into 5 cm × 5 cm pieces and stored at room temperature (20 ℃).

[0147] Heat shrinkage at 85°C: After immersing a polyester film specimen in hot water at 85°C for 10 seconds, the change in length in the transverse direction (TD), which is the main shrinkage direction, was calculated by applying Equation 2 below.

[0148] Heat shrinkage at 90°C: After immersing a polyester film specimen in hot water at 90°C for 10 seconds, the change in length in the transverse direction (TD), which is the main shrinkage direction, was calculated by applying Equation 2 below.

[0149] [Formula 2]

[0150] Heat shrinkage (%) = {(F S1 -F S2 ) / F S1} × 100

[0151] In the above equation 2,

[0152] F S1 is the transverse (TD) length of the polyester film specimen before immersion in hot water,

[0153] F S2 is the transverse (TD) length of the polyester film specimen after immersion in hot water.

[0154]

[0155] [Test Example 3] Melting temperature

[0156] Each of the polyester films manufactured in Manufacturing Examples 1 to 5 and Comparative Manufacturing Examples 1 to 3 was analyzed by differential scanning calorimetry (DSC) to determine the melting temperature (T m ) was confirmed to appear, and the results are shown in Table 1 below. The DSC analysis of the polyester film was performed as follows.

[0157] DSC analysis device: Mettler Toledo's DSC 1 model was used.

[0158] Sample preparation: Take about 6 to 10 mg of polyester film and fill an aluminum pan.

[0159] Scan conditions: DSC curves were obtained by heating from room temperature to 280 ℃ at a rate of 10 ℃ / min and annealing at 280 ℃ for 3 min.

[0160] Melting temperature determination: The glass transition temperature (T) that appears during the heating process in the obtained DSC curve g ) after the endothermic peak is the melting temperature (T m ) was defined. In addition, two or more melting temperatures (T m ) is confirmed, the melting temperature (T) is greater when the ΔH value is large. m ) was applied.

[0161]

[0162] [Test Example 4] Analysis of metal and phosphorus (P) content

[0163] Each of the polyester films manufactured in Manufacturing Examples 1 to 5 and Comparative Manufacturing Examples 1 to 3 was prepared in an amount of 0.3 g. Next, the prepared polyester films were treated with a high-pressure microwave in the presence of nitric acid and diluted with ultrapure water. Then, the polyester films were analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES) using a spectroscopic analyzer (Agilent, ICP-AES 7700S) to confirm the contents of metals and phosphorus (P). The results are shown in Table 1 below.

[0164]

[0165] [Test Example 5] Recyclability

[0166] Each of the polyester films manufactured in Manufacturing Examples 1 to 5 and Comparative Manufacturing Examples 1 to 3 was cut to 12 cm × 12 cm to prepare a polyester film specimen. Next, the prepared polyester film specimen was placed in a water bath containing water at 95°C and shrunk for 15 seconds to form a heat-shrinkable film bonded to a PET bottle. Next, the polyester film specimen and the PET bottle, which had gone through the shrinkage and drying process, were placed in a crusher and crushed to produce mixed flakes. The prepared mixed flakes were placed in warm water at 85°C (washing temperature) for 15 minutes, and the degree of opacity of the flakes from which the polyester film specimen was crushed was visually confirmed, and the results are shown in Table 1 below.

[0167] ◎: Film specimen flake opaque (excellent recyclability)

[0168] ○: Film specimen flake translucent (good recyclability)

[0169] ×: Film specimen flakes transparent (poor recyclability)

[0170]

[0171] Manufacturing Example 1 Manufacturing Example 2 Manufacturing Example 3 Manufacturing Example 4 Manufacturing Example 5 Comparative Manufacturing Example 1 Comparative Manufacturing Example 2 Comparative Manufacturing Example 3 Heat Shrinkage Rate (%) 85℃ 52% 50% 55% 55% 56% 25% 55% 45% 90℃ 67% 69% 78% 67% 65% 35% 70% 57% △H ave (% / ℃)T1T275℃80℃5.05.45.51.94.10.40.31.080℃85℃6.67.65.49.22.513.90.41.485℃90℃4.32.63.53.93.93.82.07.4H 80 - H 75 (%)25.227.127.49.420.62.21.44.8H 85 - H 80 (%)33.038.227.146.112.469.32.17.0H 90 - H 85 (%)21.512.917.419.519.519.07.037.0Inorganic content (ppm)P(P)Excluding metals2465622271003428072Phosphorus (P)1711971941115504Melting temperature (℃)167185155190205232-265Recyclability◎○○○◎○××

[0172] Referring to Table 1 above, the polyester films of Manufacturing Examples 1 to 5 (Examples 1 to 5) according to the present invention have a high heat shrinkage rate by temperature and an average haze change rate (△H ave ) can be confirmed to be controlled within the scope of the present invention.

[0173] On the other hand, it can be confirmed that the polyester film of Comparative Manufacturing Example 1 (Comparative Example 1) has a low heat shrinkage rate, making it difficult to apply as a heat shrinkable film. In addition, Comparative Manufacturing Example 2 (Comparative Example 2) has a low average haze change rate and no melting temperature, resulting in poor crystallinity. Therefore, it can be expected that fusion will occur with the plastic container when put into the recycling process, making the recycling process impossible. In addition, Comparative Manufacturing Example 3 (Comparative Example 3) does not satisfy the heat shrinkage rate at the level targeted by the present invention, and it can be expected that processability will not be good due to its high melting temperature.

Claims

1. A polyester resin comprising a diol repeating unit derived from a diol component and a dicarboxylic acid repeating unit derived from a dicarboxylic acid component, The heat shrinkage rate in the main shrinkage direction at 85 ℃ is 50% or more, When T1 is 80 ℃ and T2 is 85 ℃, the average haze change rate (ΔH) according to the following equation 1 ave ) is 0.5 to 10, polyester film: [Formula 1] ΔH ave (% / ℃) = │H T2 - H T1 │ / │T2 - T1│ In the above equation 1, H T1 is the haze of the polyester film at the T1 temperature, H T2 is the haze of the polyester film at temperature T2.

2. In paragraph 1, When T1 is 85 ℃ and T2 is 90 ℃, the average haze change rate (ΔH) according to the above equation 1 ave ) is 1 to 5, polyester film.

3. In paragraph 1, When T1 is 75 ℃ and T2 is 80 ℃, the average haze change rate (ΔH) according to the above equation 1 ave ) is 0.5 to 8, polyester film.

4. In paragraph 1, A polyester film having a haze of 10% or more at 80°C and a haze of 50% or more at 90°C.

5. In paragraph 1, Haze at 80 ℃ (H 80 ) and haze (H) at 75 ℃ 75 ) of the car (H) 80 - H 75 ) is 7 to 30%, Haze at 85 ℃ (H 85 ) and haze (H) at 80 ℃ 80 ) of the car (H) 85 - H 80 ) is 10 to 50%, Haze at 90 ℃ (H 90 ) and haze at 85 ℃ (H 85 ) of the car (H) 90 - H 85 ) of 10 to 25%, polyester film.

6. In paragraph 1, A polyester film having a metal content of 5 to 250 ppm as measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

7. In paragraph 6, A polyester film, wherein the metal comprises at least one selected from the group consisting of antimony (Sb), titanium (Ti), zinc (Zn), germanium (Ge), magnesium (Mg), and manganese (Mn).

8. In paragraph 1, A polyester film having a phosphorus (P) content of 5 to 200 ppm as measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

9. In paragraph 1, Melting temperature (T m ) Polyester film having a temperature of 230 ℃ or less.

10. In paragraph 1, A polyester film, wherein the dicarboxylic acid component comprises at least one selected from the group consisting of terephthalic acid, isophthalic acid, dimethyl phthalate, dimethyl isophthalate, dimethyl terephthalate, phthalic acid, phthalic anhydride, 2,6-naphthalene dicarboxylic acid, dimethyl 2,6-naphthalene dicarboxylate, diphenyl dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, dimethyl 1,4-cyclohexane dicarboxylate, dimethyl 1,3-cyclohexane dicarboxylate, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, glutaric acid, azelaic acid, and recycled terephthalic acid.

11. In paragraph 1, The above diol component is bis-2-hydroxyethyl terephthalate, isosorbide, neopentyl glycol, ethylene glycol, diethylene glycol, cyclohexanedimethanol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 4-(hydroxymethyl)cyclohexylmethyl-4-(hydroxymethyl)cyclohexanecarboxylate, A polyester film comprising at least one selected from the group consisting of 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol, recycled bis-2-hydroxyethyl terephthalate, recycled isosorbide, recycled neopentyl glycol, recycled ethylene glycol, recycled diethylene glycol, and recycled cyclohexanedimethanol. 12.(1) A step of manufacturing a polyester resin by polymerizing a diol component and a dicarboxylic acid component; (2) a step of manufacturing a stretched film from the polyester resin; and (3) including a step of opening and fixing the above-mentioned stretched film, The heat shrinkage rate in the main shrinkage direction at 85 ℃ is 50% or more, When T1 is 80 ℃ and T2 is 85 ℃, the average haze change rate (ΔH) according to the following equation 1 ave ) is 0.5 to 10, a method for manufacturing a polyester film: [Formula 1] ΔH ave (% / ℃) = │H T2 - H T1 │ / │T2 - T1│ In the above equation 1, H T1 is the haze of the polyester film at the T1 temperature, H T2 is the haze of the polyester film at temperature T2.