TW202126734A - Polyester film and method for reproducing polyester container using the same - Google Patents

Abstract

The embodiments relate to a polyester film, which comprises a copolymerized polyester resin comprising a diol component and a dicarboxylic acid component and has a heat shrinkage rate of 30% or more in the main shrinkage direction upon thermal treatment at a temperature of 80 DEG C for 10 seconds and a melting point of 170 DEG C or higher as measured by differential scanning calorimetry, which not only solve the environmental problems by improving the recyclability of the polyester container, but also are capable of enhancing the yield and productivity, and a process for regenerating a polyester container using the same.

Description

Polyester film and method for reproducing polyester container using the polyester film

Field of invention The specific example of the present invention relates to a polyester film and a method for reproducing a polyester container using the polyester film. The present invention not only solves the environmental problem by improving the recyclability of the polyester container, but can also increase the productivity. And productivity.

Background of the invention In recent years, as concerns about environmental issues have increased, there has been a need to solve the recycling issues of products made with thermoplastic polymers. In particular, polyethylene terephthalate—a thermoplastic resin with excellent properties in terms of heat resistance, processability, transparency, and non-toxicity—has been widely used in the production of various products, such as films, fibers, bottles, containers, etc. Etc., and efforts have been made to increase its regeneration rate.

Generally, a stretched polyolefin film or the like is attached to a container made of polyethylene terephthalate as a label. Therefore, once the container recovered from the consumer has been washed and broken, it is then thrown into liquid specific gravity separation, dehydration, drying and/or wind specific gravity separation to remove a large amount of film contained in the broken product, and then thrown into such as granulation Additional steps to obtain recycled polyester chips. However, the disadvantage is that even after the above steps, the film is not completely removed; and the recycled polyester chips are colored due to the ink contained in the film, or they agglomerate unevenly during their heat treatment.

Accordingly, a method of using a film made of a low specific gravity polymer such as polystyrene, polyethylene, polypropylene, etc. as a label has been proposed to easily perform specific gravity separation. However, due to the ink layer, its low specific gravity cannot be effectively achieved, making it difficult to completely separate the film, and it is impossible to solve the problem of the residual ink color of the regenerated slice.

Technical Problem Accordingly, the specific example of the present invention aims to provide a polyester film that can avoid aggregation caused by residual ink during the regeneration method, thereby improving the recyclability of the polyester container, and a method for recycling the polyester film The method of polyester container.

The solution to the problem In one aspect disclosed in the present invention, according to a specific example, a polyester film is provided, the polyester film includes a copolyester resin, which includes a diol component and a dicarboxylic acid component, And the polyester film has a heat shrinkage rate of 30% or higher in the main shrinkage direction after heat treatment at a temperature of 80°C for 10 seconds, and a melting point of 170°C or higher as measured by differential scanning calorimetry .

According to a specific example, a polyester film is provided, the polyester film includes a copolyester resin, which includes a diol component and a dicarboxylic acid component, and the polyester film has 15 Haze of 50% or less in minutes.

According to a specific example, there is provided a polyester film comprising a first layer and a second layer, the first layer comprising a copolyester resin comprising a diol component and a dicarboxylic acid component , The second layer contains a resin having a glass transition temperature (Tg) of 70°C or higher.

According to a specific example, there is provided a method of regenerating a polyester container, the method comprising preparing a polyester container provided with the polyester film; breaking the container provided with the polyester film to obtain a number of small pieces; and heat treatment These small pieces are used to manufacture recycled polyester chips, wherein when the small pieces are heat-treated at a temperature of 200°C to 220°C for 60 minutes to 120 minutes, the agglutination fraction is 8% or less, and the small pieces contain Several first small pieces obtained by breaking the container and several second small pieces obtained by breaking the polyester film.

Advantageous effects of the invention The polyester film according to these specific examples improves the recyclability of the polyester container, thereby solving environmental problems, and improving yield and productivity.

In addition, the method of regenerating the polyester container according to this specific example does not require a separate step of separating the polyester container and the film, thereby saving time and cost.

Best Mode for Carrying Out the Invention Hereinafter, the present invention will be explained in detail with reference to specific examples. Specific examples are not limited to those described below. Rather, they can be modified into various forms as long as the gist of the present invention is not changed.

Throughout this specification, when a part is referred to as "comprising" an element, it should be understood that, unless expressly specified otherwise, other elements may be included instead of excluding other elements.

Unless clearly indicated otherwise, all numbers and terms used in this case related to the amounts of components, reaction conditions, etc., should be understood as modified by the term "about". Polyester film

According to a specific example, there is provided a polyester film including a copolyester resin, which includes a diol component and a dicarboxylic acid component, and the polyester film has a heat treatment at a temperature of 80°C. After seconds, a thermal shrinkage rate of 30% or higher in the main shrinkage direction and a melting point of 170°C or higher as measured by differential scanning calorimetry.

According to a specific example, there is provided a polyester film comprising a copolyester resin containing a diol component and a dicarboxylic acid component, wherein after heat treatment at a temperature of 80°C for 10 seconds, the main The heat shrinkage rate in the shrinking direction is 30% or higher, and by differential scanning calorimetry, the crystallization temperature of the film is not measured or is 70°C to 95°C.

According to a specific example, the copolyester resin includes a diol component and a dicarboxylic acid component.

According to a specific example, the diol component is composed of linear or branched C ₂ to C ₁₀ diols. That is, the diol component may not contain alicyclic diol or aromatic diol.

For example, linear or branched C ₂ to C ₁₀ diols may include the following derivatives: ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,2-octaned Alcohol, 1,3-octanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2-butyl-2-ethane 1,3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentane Diol, 1,1-dimethyl-1,5-pentanediol, 1,6-hexanediol, 2-ethyl-3-methyl-1,5-hexanediol, 2-ethyl- 3-ethyl-1,5-hexanediol, 1,7-heptanediol, 2-ethyl-3-methyl-1,5-heptanediol, 2-ethyl-3-ethyl-1 ,6-Heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, or any combination thereof. But it is not limited to this.

According to a specific example, the glycol component may include at least one selected from the group consisting of ethylene glycol, diethylene glycol, cyclohexane dimethanol (CHDM), unsubstituted or Alkyl-substituted propylene glycol, unsubstituted or alkyl-substituted butanediol, unsubstituted or alkyl-substituted pentanediol, unsubstituted or alkyl-substituted hexanediol, unsubstituted or Alkyl substituted octanediol and combinations thereof.

According to a specific example, the diol component may include ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol, 1,3-propanediol, 1,2-octanediol, and 1,3-octanediol. Alcohol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 2-butyl-2-ethyl-1 ,3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,1-Dimethyl-1,5-pentanediol or a combination thereof.

According to a specific example, the diol component may be at least one selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, and cyclohexanedimethanol.

The dicarboxylic acid component may be selected from the group consisting of: aromatic dicarboxylic acids, such as terephthalic acid, dimethylterephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, phthalic acid Formic acid, etc.; aliphatic dicarboxylic acids, such as adipic acid, azelaic acid, sebacic acid, sebacic acid, etc.; cycloaliphatic dicarboxylic acids; esters thereof; and combinations thereof . Specifically, the dicarboxylic acid component may be composed of terephthalic acid, dimethylterephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, phthalic acid, or a combination thereof.

According to a specific example, the dicarboxylic acid component may include an aromatic dicarboxylic acid. For example, based on the total moles of the dicarboxylic acid component, the dicarboxylic acid component may contain at least 80 mol%, at least 90 mol%, or at least 95 mol% of terephthalic acid, dimethyl pair Phthalic acid or isophthalic acid.

According to a specific example, based on the total moles of the glycol component, the copolyester resin may contain 55 to 94 mole% of ethylene glycol. For example, based on the total moles of the glycol component, the copolyester resin may include ethylene glycol in an amount of 60 to 90 mole%, 65 to 85 mole%, or 65 to 80 mole%. If the above range is satisfied, the thermal shrinkage rate of the film prepared accordingly can be adjusted to an appropriate level, and the agglutination fraction in the subsequent regeneration step can be reduced.

According to a specific example, based on the total moles of the diol component, the copolyester resin may contain 1 to 20 mole% of diethylene glycol. For example, based on the total moles of the diol component, the copolyester resin may contain 1 to 15 mole%, 1 to 13 mole%, 1 to 10 mole%, 1.5 to 10 mole%, or 1 The amount of diethylene glycol to 8 mol%. If the above range is satisfied, the thermal shrinkage rate of the film prepared accordingly can be adjusted to an appropriate level, and the agglutination fraction in the subsequent regeneration step can be reduced.

According to a specific example, based on the total moles of the diol component, the copolyester resin may contain 5 to 35 mole% of neopentyl glycol. For example, based on the total moles of the diol component, the copolyester resin may contain 5 to 30 mole%, 7 to 35 mole%, 10 to 30 mole%, or 15 to 30 mole%. Neopentyl glycol. If the above range is satisfied, a polyester film whose heat shrinkage in the first direction and in the direction perpendicular to the first direction is not high even at high temperatures can be produced. In particular, if the content of neopentyl glycol exceeds the above-mentioned range, the film may swell excessively in the second direction compared to the first direction, so it may be wrinkled or deformed when the film is applied to the container. In addition, if the content of neopentyl glycol is less than the above range, the amorphous area is unnecessarily large, due to the low shrinkage characteristics in the second direction, the expansion coefficient will increase, although the shrinkage in the first direction may be increased. feature.

In this specification, the first direction is the main contraction direction, and may be horizontal or vertical. Specifically, the first direction may be a transverse direction, and the second direction perpendicular to the first direction may be a longitudinal direction. Alternatively, the first direction may be a longitudinal direction, and the second direction perpendicular to the first direction may be a lateral direction.

According to a specific example, based on the total moles of the diol component, the copolyester resin may contain cyclohexane dimethanol in an amount of 0 to 35 mole %. For example, based on the total moles of the diol component, the copolyester resin may contain 1 to 35 mole%, 5 to 30 mole%, 7 to 30 mole%, 10 to 30 mole%, or 15 mole%. The amount of cyclohexane dimethanol to 30 mol%. If the above range is satisfied, the thermal shrinkage rate of the film prepared accordingly can be adjusted to an appropriate level, and the agglutination fraction in the subsequent regeneration step can be reduced.

According to a specific example, the copolyester resin contains a dicarboxylic acid component and a diol component, wherein the dicarboxylic acid component can be composed of terephthalic acid, isophthalic acid or dimethyl terephthalic acid, and the diol group The fraction can be composed of (i) neopentyl glycol and (ii) ethylene glycol, diethylene glycol, cyclohexane dimethanol or a combination thereof. Specifically, the dicarboxylic acid component may be composed of terephthalic acid or dimethyl terephthalic acid, and the diol component may be composed of (i) neopentyl glycol and (ii) ethylene glycol. Alternatively, the dicarboxylic acid component may be composed of terephthalic acid, isophthalic acid or dimethyl terephthalic acid, and the diol component may be composed of (i) diethylene glycol and (ii) ethylene glycol.

If the dicarboxylic acid component in the copolyester resin is composed of terephthalic acid, isophthalic acid or dimethyl terephthalic acid, and if the diol component in the copolyester resin is composed of (i) Composed of neopentyl glycol and (ii) ethylene glycol, diethylene glycol or a combination thereof, the copolyester resin can have reduced whitening and low haze of 15% or less and is excellent in dimensional stability .

The diol component may further include monohydric alcohols. For example, it may further include isopropanol. Specifically, the copolyester resin may contain 15 to 30 mol%, 18 to 25 mol%, or 20 to 25 mol% of the monohydric alcohol based on the total moles of the diol component. But it is not limited to this.

The above-mentioned dicarboxylic acid component and diol component are subjected to a transesterification reaction, followed by polymerization, thereby forming a copolyester resin. Specifically, at least one catalyst selected from the group consisting of manganese acetate, calcium acetate, and zinc acetate can be used as a catalyst for the transesterification reaction. The content of the catalyst may be 0.02 to 0.2% by weight based on the total weight of the dicarboxylic acid compound. After the transesterification reaction is completed, at least one additive selected from silicon dioxide, potassium and magnesium; stabilizer such as trimethyl phosphate; polymerization catalyst selected from antimony trioxide and tetrabutyl titanate; etc. can be selected It can be added in order to react, thereby preparing a copolyester resin composition.

According to a specific example, after heat treatment at a temperature of 80° C. for 10 seconds, the polyester film may have a heat shrinkage rate of 30% or higher in the first direction. For example, after heat treatment at a temperature of 80°C for 10 seconds, the polyester film may have 40% or higher, 45% or higher, 50% or higher, 30% to 85%, 40% in the first direction. To 80% or 50% to 80% thermal shrinkage. If the above range is satisfied, it is easy to label the polyester film on the surface of the container.

According to a specific example, after heat treatment at a temperature of 90° C. for 10 seconds, the polyester film may have a heat shrinkage rate of 50% or higher in the first direction. For example, after heat treatment at a temperature of 90°C for 10 seconds, the polyester film may have 55% or higher, 60% or higher, 70% or higher, 50% to 90%, 60% in the first direction. To 85%, 70% to 85%, or 70% to 80% heat shrinkage rate. If the above range is satisfied, it is easy to label the polyester film on the surface of the container.

According to a specific example, after heat treatment at a temperature of 70° C. for 10 seconds, the polyester film may have a heat shrinkage rate of 5% to 55% in the first direction. For example, after heat treatment at a temperature of 70°C for 10 seconds, the polyester film may have a heat shrinkage of 5% to 50%, 10% to 50%, 20% to 45%, or 25% to 40% in the first direction. Rate. If the above range is satisfied, it is easy to label the polyester film on the surface of the container.

According to a specific example, after heat treatment at a temperature of 100° C. for 10 seconds, the polyester film may have a heat shrinkage rate of 30% or higher in the first direction. For example, after heat treatment at a temperature of 100°C for 10 seconds, the polyester film may have 35% or more, 40% or more, 50% or more, 30% to 90%, 30% in the first direction. To 80%, 40% to 80%, 45% to 80%, or 50% to 80% thermal shrinkage. If the above range is satisfied, it is easy to label the polyester film on the surface of the container.

According to a specific example, in the temperature range of 0.35 × Tm°C to 0.40 × Tm°C, the increase rate of the heat shrinkage rate in the first direction is 2.5%/°C to 4.0%/°C, and in the temperature range of 0.45 × Tm°C to 0.50 × Tm°C In the temperature range of Tm°C, the increase rate of the thermal shrinkage in the first direction is 0.1%/°C to 1.0%/°C.

According to a specific example, the polyester film has a melting point (Tm) of 170° C. or higher as measured by differential scanning calorimetry. For example, measured by differential scanning calorimetry, the polyester film can have a temperature of 175°C or higher, 170°C or higher, specifically, 170°C to 230°C, 170°C to 200°C, or 175°C to Melting point of 200°C. If the above range is satisfied, the agglutination fraction in the subsequent regeneration step can be reduced.

According to a specific example, by differential scanning calorimetry, the crystallization temperature of the polyester film is not measured or is measured to be 70°C to 95°C. For example, by differential scanning calorimetry, the crystallization temperature of the polyester film can be 70°C to 93°C, 75°C to 93°C, or 75°C to 90°C. If the above range is satisfied, the agglutination fraction in the subsequent regeneration step can be reduced.

According to a specific example, measured at the crystallization temperature (Tc), the heat of crystallization of the polyester film can be 0.01 to 50 J/g. For example, the heat of crystallization of the polyester film can be 0.01 to 40 J/g, 0.05 to 30 J/g, 0.1 to 20 J/g, 0.1 to 10 J/g, 0.1 to 8 J/g, or 0.1 to 5. J/g. If the above range is satisfied, the agglutination fraction in the subsequent regeneration step can be reduced.

According to a specific example, the polyester film has a glass transition temperature (Tg) of 60° C. or higher as measured by differential scanning calorimetry. For example, measured by differential scanning calorimetry, polyester film has 65°C or higher, 68°C or higher, 70°C or higher, 60°C to 150°C, 65°C to 150°C, 69°C To 150°C, 70°C to 120°C or 65°C to 80°C glass transition temperature. If the above range is satisfied, the agglutination fraction in the subsequent regeneration step can be reduced.

According to a specific example, the polyester film may have a haze of 10% or less. For example, the polyester film may have a haze of 8% or lower, 7% or lower, or 5% or lower.

According to a specific example, the polyester film may have a haze of 50% or less when immersed in a 0.5% to 3% NaOH aqueous solution for 5 minutes to 30 minutes. More specifically, the polyester film may have 10% or less, 7% or less, 5% or less, 30% to 50%, 35% to 45 percent when immersed in 1% NaOH aqueous solution for 15 minutes. % Or 40% to 45% haze. For example, the polyester film can be immersed in a 0.5% to 2.5% or 0.5% to 2% NaOH aqueous solution at a temperature of 70°C to 90°C, 75°C to 90°C or 85°C for 5 minutes to 20 minutes Or from 10 minutes to 15 minutes, the haze is 9% or lower, 7% or lower, 5% or lower, 30% to 50%, 35% to 45%, or 40% to 45%. If the above range is satisfied, the agglutination fraction in the subsequent regeneration step can be reduced.

According to a specific example, when the polyester film is immersed in a 0.5% to 3% NaOH aqueous solution for 5 minutes to 30 minutes, the haze difference before and after immersion may be 20% to 50%. For example, when the polyester film is immersed in a 1% NaOH aqueous solution for 15 minutes, the haze difference before and after immersion may be 20% to 40%, 25% to 40%, or 30% to 40%. If the above range is satisfied, the agglutination fraction in the subsequent regeneration step can be reduced.

Specifically, when the polyester film is immersed in a 1% NaOH aqueous solution for 15 minutes, if the haze difference before and after immersion is 20% to 50%, the melting point measured by differential scanning calorimetry can be 140°C or higher. For example, when the polyester film is immersed in a 1% NaOH aqueous solution for 15 minutes, if the haze difference before and after the immersion is 20% to 40%, 25% to 40%, or 30% to 40%, the difference The melting point measured by scanning calorimetry can be 140°C to 230°C, 145°C to 200°C, or 150°C to 200°C.

According to a specific example, the thickness of the polyester film may be 30 to 100 μm. For example, the thickness of the polyester film may be 30 to 95 μm or 35 to 90 μm. If the above range is satisfied, the shrinkage uniformity is excellent.

According to a specific example, there is provided a polyester film comprising a first layer and a second layer, the first layer comprising a copolyester resin comprising a diol component and a dicarboxylic acid component, and the second layer The second layer contains a resin having a glass transition temperature (Tg) of 70°C or higher.

According to a specific example, the first layer includes a copolymerized polyester resin, which includes a diol component and a dicarboxylic acid component.

The details of the copolymer polyester resin are as described above.

According to a specific example, the thickness of the first layer may be 30 to 100 µm. For example, the thickness of the first layer can be 30 to 90 µm, 30 to 85 µm, 35 to 90 µm, or 40 to 80 µm.

According to a specific example, the second layer includes a resin having a glass transition temperature (Tg) of 70°C or higher. For example, the second layer may include a temperature of 70°C or higher, 75°C or higher, 80°C or higher, 70°C to 350°C, 70°C to 330°C, 70°C to 300°C, 75°C to 250°C ℃, 75 ℃ to 200 ℃, 75 ℃ to 180 ℃, 75 ℃ to 150 ℃ or 75 ℃ to 120 ℃ glass transition temperature resin.

The second layer containing a resin that satisfies the glass transition temperature range increases the heat shrinkage rate of the polyester film and reduces the agglomeration fraction in the subsequent regeneration step.

According to a specific example, the second layer may include at least one resin selected from the group consisting of polyethylene terephthalate (PET), polyethylene cyclohexane dimethyl terephthalate (PCT ), polymethyl methacrylate (PMMA), co-polyethylene terephthalate (co-PET), polyethylene naphthalate (PEN), polyether agglomerate (PES), polycarbonate (PC ), polystyrene (PS), polyamide (PA) and polyimide (PI).

According to a specific example, the thickness of the second layer may be 1 to 100 nm. For example, the thickness of the second layer can be 1 to 80 nm, 5 to 100 nm, 10 to 100 nm, 20 to 100 nm, 20 to 50 nm, 30 to 100 nm, 20 to 50 nm, 1 to 30 nm , 5 to 10 nm, 5 to 20 nm, or 1 to 20 nm.

According to a specific example, the polyester film may be composed of 2 to 100 layers by laminating the first layer and the second layer. For example, the polyester film can be composed of 2 to 100 layers, 3 to 100 layers, 4 to 100 layers, 5 to 100 layers, 2 to 80 layers, 2 to 50 layers by alternately laminating the first layer and the second layer. Layers, 3 to 80 layers, 3 to 50 layers, 3 to 40 layers, or 3 to 30 layers. Specifically, at least one of the outermost layers of the polyester film is composed of the second layer, which is advantageous in that it is possible to reduce the agglutination fraction in the subsequent regeneration step.

According to a specific example, the polyester film can be composed of three layers by laminating a first layer and a second layer, and the second layer can be located at the outermost layer. For example, the polyester film can be composed of 3 to 80 layers, 3 to 50 layers, 3 to 40 layers, or 3 to 30 layers by alternately laminating the first layer and the second layer. The outermost layer of the polyester film At least one of them is the second layer. Specifically, the second layer containing a resin having a glass transition temperature (Tg) of 70°C or higher is the outermost layer of the polyester film, which is advantageous in that it is possible to reduce the agglomeration fraction in the subsequent regeneration step .

According to a specific example, the polyester film including the first layer and the second layer may have a melting point (Tm) of 150° C. or higher by measuring by differential scanning calorimetry. For example, measured by differential scanning calorimetry, the melting point of the polyester film can be 155°C or higher, 160°C or higher, 165°C or higher, specifically, 150°C to 230°C, 155°C ℃ to 200 ℃, 160 ℃ to 200 ℃, 165 ℃ to 200 ℃ or 165 ℃ to 180 ℃. If the above range is satisfied, the agglutination fraction in the subsequent regeneration step can be reduced. Method for preparing polyester film (1)

The polyester film can be prepared from a copolyester resin.

Specifically, the copolyester resin may be melt-extruded through a T-die at 260°C to 300°C or 270°C to 290°C, and then cooled to obtain an unstretched sheet. The unstretched sheet is passed through a roller at a speed of 10 m/min to 110 m/min or 50 m/min to 90 m/min, and then stretched to obtain a stretched sheet, which is heat-set To prepare polyester film.

It can be preheated at 90°C to 120°C for 0.01 to 1 minute. For example, the preheating temperature (T1) may be 95°C to 115°C or 97°C to 113°C, and the preheating time may be 0.05 minutes to 0.5 minutes or 0.08 minutes to 0.2 minutes. But these are not limited to this.

According to a specific example, the stretching can be performed in a first direction or a second direction perpendicular to the first direction. Alternatively, stretching can be performed in a first direction, followed by a second direction. Specifically, the stretching may be performed 3 to 5 times in a first direction or in a second direction perpendicular to the first direction at a temperature lower than the preheating temperature (T1) by at least 20°C. For example, stretching can be performed at a stretching temperature of 60°C to 90°C, 70°C to 90°C, or 80°C to 90°C in a first direction or in a second direction perpendicular to the first direction. To 4.5 times, 3.5 to 4.5 times or 4 to 4.5 times. But it is not limited to this.

Heat setting can be annealed at 70°C to 95°C for 0.01 minute to 1 minute. For example, the heat setting temperature (T2) can be 75°C to 95°C, 75°C to 90°C, 80°C to 90°C, 85°C to 95°C, or 85°C to 90°C, and the heat setting time can be 0.05 minutes to 0.5 minutes or 0.08 minutes to 0.2 minutes. But these are not limited to this.

According to a specific example, the preheating temperature (T1)-the heat setting temperature (T2) can be 10°C to 40°C. For example, T1-T2 can be 13°C to 35°C, 11°C to 34°C, 15°C to 34°C, or 20°C to 34°C. If the above range is satisfied, the thermal shrinkage rate in the first direction and the second direction can be effectively controlled. Method for preparing polyester film (2)

The polyester film may be prepared from a copolyester resin and a resin having a glass transition temperature (Tg) of 70°C or higher.

Specifically, the method may include (a) preparing a sheet in which a first layer and a second layer are laminated by a copolyester resin and a resin having a glass transition temperature (Tg) of 70°C or higher; (b) stretching the laminated sheet in at least one of a first direction and a second direction perpendicular to the first direction; (c) heat setting the laminated sheet; and ( d) Relax the heat-set sheet. Step (a)

According to a specific example, a sheet can be prepared in which a first layer and a second layer are laminated. Specifically, the copolyester resin and the resin having a glass transition temperature (Tg) of 70°C or higher may be melt-extruded through an extruder, or the copolyester resin may be melt-extruded and then will have a glass transition temperature (Tg) of 70°C or higher. A resin with a high glass transition temperature (Tg) is coated on it and then dried to prepare a sheet in which a first layer and a second layer are alternately laminated. More specifically, the sheet prepared in step (a) can be prepared by co-extrusion co-polyester resin and resin having a glass transition temperature (Tg) of 70° C. or higher, or extrusion co-polymerization The ester resin is then thrown into the coating step to prepare a sheet in which a first layer and a second layer are laminated. The coextrusion or coating step can be performed by conventional steps.

According to a specific example, the formation and lamination of the first layer and the second layer can be performed simultaneously via coextrusion.

According to a specific example, according to a specific example, the sheet prepared in step (a) may be a sheet in which the first layer and the second layer are alternately laminated. In addition, the outermost layer of the sheet prepared in step (a) may be the second layer.

Melt extrusion can be performed at a temperature of 260°C to 300°C or 270°C to 290°C. The melt-extruded copolyester resin and the resin having a glass transition temperature (Tg) of 70° C. or higher may be laminated via a multilayer feed block to form a sheet. Alternatively, a copolyester resin and a resin having a glass transition temperature (Tg) of 70°C or higher can be extruded into multiple layers via two extruders, and then the laminated multiple layers are introduced into the T-shaped Die to form the sheet. Step (b)

According to a specific example, in step (b), a step of stretching the sheet may be performed in at least one of a first direction or a second direction perpendicular to the first direction.

Specifically, before stretching, the sheet may be preheated at 90°C to 140°C for 0.01 minute to 1 minute. For example, the preheating temperature (T1) may be 95°C to 115°C or 97°C to 113°C, and the preheating time may be 0.05 minutes to 0.5 minutes or 0.08 minutes to 0.2 minutes. But these are not limited to this.

Stretching can be performed by biaxial stretching. For example, it can be performed by a simultaneous biaxial stretching method or a sequential biaxial stretching method in a first direction and a second direction. Preferably, it can be performed by a sequential biaxial stretching method, in which the stretching is first performed in one direction, and then the stretching is performed in a direction perpendicular to it. For example, the sheet can be stretched in a first direction and then stretched in a second direction.

According to a specific example, the stretching can be performed in a first direction or a second direction perpendicular to the first direction. Alternatively, stretching can be performed in a first direction, followed by a second direction. Specifically, the stretching may be performed 3 to 5 times in a first direction or in a second direction perpendicular to the first direction at a temperature lower than the preheating temperature (T1) by at least 20°C. For example, stretching can be performed at a stretching temperature of 60°C to 120°C, 60°C to 90°C, 70°C to 90°C, or 80°C to 90°C in a first direction or in a direction perpendicular to the first direction. A second direction is performed 3 to 4.5 times, 3.5 to 4.5 times, or 4 to 4.5 times. But it is not limited to this. Step (c)

According to a specific example, in step (c), the stretched sheet can be heat set.

Specifically, the heat setting can be annealed at 70°C to 95°C for 0.01 minute to 1 minute. For example, the heat setting temperature (T2) may be 75°C to 95°C or 75°C to 90°C, and the heat setting time may be 0.05 minutes to 0.5 minutes or 0.08 minutes to 0.2 minutes. But these are not limited to this.

According to a specific example, the preheating temperature (T1)-the heat setting temperature (T2) can be 10°C to 50°C. For example, T1-T2 may be 13°C to 35°C, 10°C to 34°C, 15°C to 34°C, 10°C to 46°C, or 20°C to 46°C. If the above range is satisfied, the thermal shrinkage rate in the first direction and in the second direction can be effectively controlled. Step (d)

According to a specific example, in step (d), the heat-set sheet can be relaxed. Specifically, the heat-set sheet can be relaxed in a first direction or in a second direction perpendicular to the first direction.

Relaxation can be performed at a relaxation rate of 0.1% to 10%, 0.5% to 8%, 1% to 5%, or 1% to 3%. In addition, relaxation can be performed for 1 second to 1 minute, 2 seconds to 30 seconds, or 3 seconds to 10 seconds. A method of reproducing a polyester container

According to a specific example, there is provided a method of regenerating a polyester container, the method comprising preparing a polyester container provided with the polyester film; breaking the container provided with the polyester film to obtain a number of small pieces; and The small pieces are heat-treated to produce recycled polyester chips, wherein when the small pieces are heat-treated at a temperature of 200°C to 220°C for 60 minutes to 120 minutes, the agglutination fraction is 8% or less, and the small pieces contain Several first small pieces obtained by breaking the container and several second small pieces obtained by breaking the polyester film.

Figure 1 schematically depicts a method of regenerating a polyester container according to a specific example. Specifically, Figure 1 illustrates (1) preparing a polyester container provided with a polyester film; (2) breaking the container provided with a polyester film to obtain several small pieces; and (3) heat treating the small pieces to manufacture Recycled polyester chips. step 1)

In step (1), a polyester container provided with a polyester film is prepared. Specifically, in step (1), a waste polyester container provided with a polyester film is prepared.

The details of the polyester film are as described above.

In a polyester container provided with a polyester film, the polyester film may be disposed on the outer surface of the polyester container. Specifically, the outer surface of the container is covered with a polyester film, and the polyester film can be shrunk by steam or hot air to wrap the outer surface of the container. In such an event, the polyester film may have an ink layer formed by a process such as printing before heat shrinking.

According to a specific example, the second polyester film provided in the polyester container can contact the polyester container. For example, when the polyester film is a laminated film composed of a first layer and a second layer, the second layer may contact the polyester container. If the second layer of polyester film contacts the polyester container, it is possible to reduce the agglutination fraction in the subsequent regeneration step.

Generally speaking, recycled waste is mixed with containers, metals, glass and plastics. Once the waste is washed, the polyester containers are sorted. Subsequently, the container can be thrown into the following process: mechanically tear or cut the film covering the container to remove it. Alternatively, once the container has been washed and broken, it is then subjected to liquid specific gravity separation, dehydration, drying and/or air specific gravity separation, and then to an additional step such as granulation. In such incidents, the quality of the manufactured recycled polyester chips may be deteriorated due to the residual film and the ink layer formed on the residual film.

Conversely, even without an additional process for removing the film, it is possible to manufacture recycled polyester chips from a container provided with a polyester film according to this specific example. Therefore, time and cost are saved.

According to a specific example, based on the total weight of the polyester container, the polyester container may contain at least 90% by weight of polyester resin. Specifically, the polyester container may be a container containing polyethylene terephthalate, and may contain 90% by weight or more, 95% by weight or more, or 99% by weight or more based on the total weight of the polyester container. More polyethylene terephthalate.

According to a specific example, the method may include immersing a polyester container provided with a film in a 0.5% to 3% NaOH aqueous solution for 5 minutes to 30 minutes. For example, the method may include immersing a polyester container provided with a film in a 0.5% to 2.5% or 1% to 0.5% NaOH aqueous solution for 5 minutes to 25 minutes or 10 minutes to 20 minutes. Step (2)

In step (2), a polyester container provided with the polyester film is broken to obtain several small pieces. The polyester container prepared in step (1) contains the polyester film, which can be broken to obtain several small pieces. In such an event, the small pieces include a plurality of first small pieces obtained by breaking the polyester container and a plurality of second small pieces obtained by breaking the polyester film.

According to a specific example, the particle size of the first small piece may be 0.1-20 mm, and the particle size of the second small piece may be 0.1-20 mm. For example, the particle size of the first small piece may be 0.5 to 15 mm, 1 to 15 mm, or 2 to 10 mm, and the particle size of the second small piece may be 0.5 to 15 mm, 1 to 15 mm, or 2 to 10 mm. Step (3)

In step (3), the small pieces are heat-treated to produce recycled polyester chips.

The heat treatment can be performed at 200°C to 220°C for 60 minutes to 120 minutes. For example, the heat treatment may be performed at 200°C to 215°C or 205°C to 220°C for 70 minutes to 120 minutes or 80 minutes to 120 minutes.

Recycled polyester chips containing these small pieces can be obtained after the heat treatment step. Specifically, a recycled polyester chip containing the first small pieces and the second small pieces can be obtained. For example, these small pieces can be melt-extruded and cut to obtain recycled polyester chips.

According to a specific example, the small pieces can be washed before the heat treatment of the small pieces. For example, the small pieces can be washed with 0.5% to 3% NaOH aqueous solution at 80°C to 97°C for 5 minutes to 30 minutes. A part or all of the ink layer remaining in the small pieces can be removed by performing the washing.

According to a specific example, after the washing step, the small pieces can be dried at 60°C to 175°C for 10 minutes to 30 minutes. Recycled polyester chips

According to a specific example, the recycled polyester chip may include a plurality of first small chips and a plurality of second small chips, the first small chips include polyethylene terephthalate, and the second small chips include copolyester resin.

According to a specific example, recycled polyester chips may have an inherent viscosity (IV) of 0.60 dl/g or higher. For example, recycled polyester chips can have 0.63 dl/g or higher, 0.65 dl/g or higher, 0.70 dl/g or higher, 0.75 dl/g or higher, 0.60 to 3.00 dl/g, 0.60 Intrinsic viscosity (IV) to 2.0 dl/g or 0.65 to 1.0 dl/g.

According to a specific example, when the small pieces are heat-treated at a temperature of 200° C. to 220° C. for 60 minutes to 120 minutes, the agglutination fraction may be 8% or less. More specifically, when the small pieces are heat-treated at a temperature of 210° C. for 90 minutes, the agglutination fraction can be 8% or less, 6% or less, 5% or less, 4% or less, 3 % Or less, 2% or less, 0.1% to 8%, 0.5% to 6%, or 1% to 6%. For example, when the small pieces are heat-treated at a temperature of 200°C to 220°C for 60 minutes to 120 minutes, the agglutination fraction may be 8% or less, 6% or less, 5% or less, 4% Or less, 3% or less, 2% or less, 0.1% to 8%, 0.5% to 6%, 1% to 6%, or 1% to 5%.

Agglutination refers to aggregates that can be formed from these small pieces. The size of the agglomerate may be, for example, at least three times the size of the plate-like particles. The agglutination fraction refers to the fraction of agglomerates based on the total weight of these small pieces. For example, the small pieces can be passed through a sieve and heat-treated. At this time, as these small pieces aggregate, aggregates may form. The agglomerates can be separated by passing through the sieve again. The weight ratio of the agglomerates can be calculated based on the total weight of the heat-treated small pieces by measuring the weight of the agglomerates thus obtained, as the agglutination fraction.

Therefore, the higher the value of the pulverization fraction, the greater the degree of entanglement between the first small piece and the second small piece, and the quality of the regenerated slice is reduced. However, the second small piece is obtained by smashing the polyester film according to this embodiment, thereby effectively reducing or avoiding agglomeration and improving the quality of recycled polyester chips.

According to a specific example, based on the total weight of the recycled polyester chips, the recycled polyester chips may contain 70 to 99% by weight of polyethylene terephthalate and 1 to 30% by weight of copolyester resin. For example, based on the total weight of the recycled polyester chips, the recycled polyester chips may contain 80 to 99% by weight, 90 to 99% by weight, or 95 to 99% by weight of polyethylene terephthalate and 1 to 28% by weight. % Or 3 to 25% by weight of copolyester resin.

The details of the copolymer polyester resin are as described above. Invention Mode

Hereinafter, the present invention will be explained in more detail with reference to the following examples. However, these embodiments are described to illustrate the present invention, and the scope of the present invention is not limited thereto. [ Example 1-1] <Preparation of copolyester resin>

A stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser was filled with 100 mol% terephthalic acid (TA) as the dicarboxylic acid component, and 80 mol% ethylene glycol (EG), 15 mol% Ear% neopentyl glycol (NPG) and 5 mol% diethylene glycol (DEG) are used as glycol components. Subsequently, 0.05 mol% (based on the acid component) zinc acetate as a transesterification catalyst was added thereto. The transesterification reaction is carried out while the methanol is removed by distillation. Then, 0.025 mol% (based on the acid component) antimony trioxide as a polycondensation catalyst was added, and a polycondensation reaction was performed at 280° C. under a reduced pressure of 26.6 Pa (0.2 Torr) to obtain a copolyester resin. ＜Preparation of polyester film＞

The copolyester resin was fed into the extruder, and then melt extruded through a T-die at 280°C. Then, it was wound around a rotating metal roll cooled to a surface temperature of 30°C to obtain an unstretched film having a thickness of 204 μm. Here, the winding speed of the unstretched film (the rotation speed of the metal roll) is 54 m/min.

The unstretched film is continuously wound around multiple rotating rolls for preheating. The longitudinally stretched film was stretched 5 times in the transverse direction at 96°C. Then, while heating the film to 81° C. using an infrared heater, the film was heat-set in the lateral direction to obtain a polyester film having a thickness of 41 μm. <Preparation of polyester container with polyester film>

The outer surface of the polyethylene terephthalate container (PET container, 30 g) was wrapped with the polyester film (1 g) prepared above. The polyester film was shrunk in hot air at a temperature of 90°C to obtain a polyester container provided with the polyester film. ＜Method of Recycled Polyester Container＞

The container provided with the polyester film is broken with a crusher to obtain several small pieces. These small pieces were washed with water, and then washed with an etching washing solution (a mixture of a 0.3% by weight Triton X-100 solution and a 1.0% by weight NaOH solution) in a 85°C to 90°C bath with stirring at 880 rpm for 15 minutes.

Then, the small pieces were washed with water at room temperature to remove the remaining corrosion washing solution, dried at 160°C for 20 minutes, and then heat-treated at 210°C to manufacture recycled polyester chips. [ Examples 1-2 to 1-4 and Comparative Example 1-1]

Recycled polyester chips were prepared in the same manner as in Example 1-1, except that the composition, content, and heat setting temperature were changed as shown in Table 1 below. [Table 1] DMT (mole%) EG (mol%) NPG (mol%) DEG (mol%) CHDM (mol%) Horizontal stretching temperature (℃) Heat setting temperature (℃) Ex. 1-1 100 80 15 5 - 96 81 Ex. 1-2 100 70 25 5 - 96 81 Ex. 1-3 100 70 25 5 - 96 78 Ex. 1-4 100 70 25 5 - 96 75 C. Ex. 1-1 100 70 - 5 25 96 81 *CHDM: Cyclohexane dimethanol [ Examples 2-1 to 2-4 and Comparative Example 2-1]

Recycled polyester chips were prepared in the same manner as in Example 1-1, except that the composition, content, and heat setting temperature were changed as shown in Table 2 below. [Table 2] DMT (mole%) EG (mol%) NPG (mol%) DEG (mol%) CHDM (mol%) Horizontal stretching temperature (℃) Heat setting temperature (℃) Ex. 2-1 100 80 15 5 - 96 81 Ex. 2-2 100 75 20 5 - 96 81 Ex. 2-3 100 70 25 5 - 96 81 Ex. 2-4 100 70 30 5 - 96 81 C. Ex. 2-1 100 70 - 5 25 96 81 [ Example 3-1] <Preparation of copolyester resin>

A stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser was filled with 100 mol% terephthalic acid (TA) as the dicarboxylic acid component, and 80 mol% ethylene glycol (EG) and 17 mol% Ear% neopentyl glycol (NPG) and 5 mol% diethylene glycol (DEG) are used as glycol components. Subsequently, 0.05 mol% (based on the acid component) zinc acetate as a transesterification catalyst was added thereto. The transesterification reaction is carried out while the methanol is removed by distillation. Then, 0.025 mol% (based on the acid component) antimony trioxide as a polycondensation catalyst was added, and a polycondensation reaction was performed at 280° C. under a reduced pressure of 26.6 Pa (0.2 Torr) to obtain a copolyester resin. ＜Preparation of polyester film＞

The copolyester resin was fed into the extruder, and then melt extruded through a T-die at 280°C. Then, it was wound around a rotating metal roll cooled to a surface temperature of 30°C to obtain an unstretched film having a thickness of 204 μm. Here, the winding speed of the unstretched film (the rotation speed of the metal roll) is 54 m/min.

The unstretched film is continuously wound around multiple rotating rolls, and preheated at 100°C to 110°C for 0.1 minutes. The longitudinally stretched film was stretched 5 times in the transverse direction at 75°C. Then, while heating the film to 85°C using an infrared heater, the film was annealed in the second direction to obtain a polyester film having a thickness of 40 µm. <Preparation of polyester container with polyester film>

The outer surface of the polyethylene terephthalate container (PET container, 30 g) was wrapped with the polyester film (1 g) prepared above. The polyester film was shrunk in hot air at a temperature of 90°C to obtain a polyester container provided with the polyester film. ＜Method of Recycled Polyester Container＞

The container provided with the polyester film is broken with a crusher to obtain small pieces. These small pieces were washed with water, and then washed with an etching washing solution (a mixture of a 0.3% by weight Triton X-100 solution and a 1.0% by weight NaOH solution) in a 85°C to 90°C bath with stirring at 880 rpm for 15 minutes.

Then, the small pieces were washed with water at room temperature to remove the remaining corrosion washing solution, dried at 160°C for 20 minutes, and then heat-treated at 210°C to manufacture recycled polyester chips. [ Examples 3-2 to 3-5 and Comparative Example 3-1]

Recycled polyester chips were prepared in the same manner as in Example 3-1, except that the composition, content, and heat setting temperature were changed as shown in Table 3 below. [table 3] TA (mol%) EG (mol%) NPG (mol%) DEG (mol%) CHDM (mol%) Horizontal stretching temperature (℃) Heat setting temperature (℃) Ex. 3-1 100 80 17 5 - 75 85 Ex. 3-2 100 75 20 5 - 76 85 Ex. 3-3 100 70 25 5 - 76 83 Ex. 3-4 100 68.5 30 1.5 - 77 85 Ex. 3-5 100 73 - 10 17 75 86 C. Ex. 3-1 100 68.5 - 1.5 30 76 84 [ Example 4-1] <Preparation of copolyester resin>

A stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser was filled with 100 mol% terephthalic acid (TA) as the dicarboxylic acid component, and 68.5 mol% ethylene glycol (EG), 30 mol% Ear% cyclohexane dimethanol (CHDM) and 1.5 mol% diethylene glycol (DEG) are used as diol components. Subsequently, 0.05 mol% (based on the acid component) zinc acetate as a transesterification catalyst was added thereto. The transesterification reaction is carried out while the methanol is removed by distillation. Then, 0.025 mol% (based on the acid component) antimony trioxide as a polycondensation catalyst was added, and a polycondensation reaction was performed at 280° C. under a reduced pressure of 26.6 Pa (0.2 Torr) to obtain a copolyester resin. ＜Preparation of polyester film＞

The copolyester resin was fed into an extruder, melt-extruded through a T-die at 280°C, and then cooled. Polyethylene terephthalate (PET 1) having a glass transition temperature of 70°C or higher was coated thereon to obtain an unstretched sheet. The unstretched sheet was preheated at 100°C to 110°C for 0.1 minutes while being transported at a speed of 55 m/min, stretched 3.0 times in the transverse direction at 75°C, and then heat-set at 75°C for 0.1 minutes, To obtain a polyester film with a thickness of 40 µm. <Preparation of polyester container with polyester film>

The outer surface of the polyethylene terephthalate container (PET container, 30 g) was wrapped with the polyester film (1 g) prepared above. The polyester film was shrunk in hot air at a temperature of 90°C to obtain a polyester container provided with the polyester film. At this time, the second layer of polyester film was brought into contact with the polyethylene terephthalate container. ＜Method of Recycled Polyester Container＞

The container provided with the polyester film is broken with a crusher to obtain small pieces. These small pieces were washed with water, and then washed with an etching washing solution (a mixture of a 0.3% by weight Triton X-100 solution and a 1.0% by weight NaOH solution) in a 85°C to 90°C bath with stirring at 880 rpm for 15 minutes.

Then, the small pieces were washed with water at room temperature to remove the remaining corrosion washing solution, dried at 160°C for 20 minutes, and then heat-treated at 210°C to manufacture recycled polyester chips. [ Examples 4-2 to 4-8 and Comparative Examples 4-1 to 4-2]

Recycled polyester chips were prepared in the same manner as in Example 4-1, except that the composition, content, and heat setting temperature were changed as shown in Table 4 below, and in Examples 4-3, 4-4, and 4- In 7 and 4-8, the co-polyester resin and a resin having a glass transition temperature (Tg) of 70°C or higher were co-extruded and laminated via two extruders. [Table 4] Number of layers level one Second floor Horizontal stretching temperature (℃) Heat setting temperature (℃) TA (mol%) EG (mol%) NPG (mol%) DEG (mol%) CHDM (mol%) Ex. 4-1 2 layer 100 68.5 - 1.5 30 PET 1 85 75 Ex. 4-2 100 65 30 5 - PET 2 84 74 Ex. 4-3 100 68.5 - 1.5 30 PCT 85 75 Ex. 4-4 100 65 30 5 - PEN 84 74 Ex. 4-5 3 layers 100 68.5 - 1.5 30 PET 1 85 75 Ex. 4-6 100 65 30 5 - PET 2 84 74 Ex. 4-7 100 68.5 - 1.5 30 PCT 96 75 Ex. 4-8 100 65 30 5 - PEN 120 74 C. Ex. 4-1 Single layer 100 68.5 - 1.5 30 - 85 75 C. Ex. 4-2 Single layer 100 65 30 5 - - 84 74 *NPG: Neopentyl glycol *PET 1: Polyethylene terephthalate (Goo Chemical, Z687) (Glass transition temperature (Tg): 100°C) *PET 2: Polyethylene terephthalate (Goo Chemical, Z690) (Glass transition temperature (Tg): 110°C) *PCT: Polycyclohexyl dimethyl terephthalate (Glass transition temperature (Tg): 96°C) *PEN: Polyethylene naphthalate (Glass transition temperature (Tg): 120°C) *Laminated structure of two layers: Second layer/First layer*Laminated structure of three layers: Second layer/First layer/Second layer [ Evaluation Example 1 : Evaluation of Thermal Shrinkage Rate]

The polyester film (300 mm×15 mm) prepared above was immersed in a water bath preheated to 80°C, 90°C, or 100°C for 10 seconds. After removing the water at room temperature, the heat shrinkage rate is calculated by the following formula.

Thermal shrinkage (%) = [(film sample length before heat treatment (mm)-film sample length after heat treatment (mm) / film sample length before heat treatment (mm)] × 100 [ Evaluation Example 2 : Tg , Tc , Tm and heat of crystallization evaluation]

While increasing the temperature from 30°C to 250°C at a rate of 10°C/min, differential scanning calorimetry-Mettler Toledo DSC 1 was used to measure the endothermic and exothermic heat of the polyester film (10 mg) prepared above, respectively. In the measurement results, the first endothermic temperature is the glass transition temperature (Tg), the exothermic temperature measured after Tg is the crystallization temperature (Tc), and the endothermic temperature measured after Tc is the melting point (Tm). The integral at Tc is calculated as the heat of crystallization. The greater the value of the heat of crystallization, the faster the crystallization rate and the higher the transfer rate to the crystalline phase. [ Evaluation Example 3 : Evaluation of Agglutination]

The small pieces prepared above were passed through a 0.625" sieve. The 1 kg small pieces sieved in this manner were exposed in an oven at 210°C for 90 minutes. The pieces were allowed to cool to room temperature and passed through a 625" sieve. The weight of the agglomerates filtered in this way is measured and calculated as a percentage of the total weight of the small pieces. [ Evaluation Example 4 : Evaluation of Inherent Viscosity]

The regenerated polyester chips prepared above were dissolved in o-chlorophenol at 100°C, and the inherent viscosity (IV) was measured by measuring the dripping time of the sample in a constant temperature bath at 35°C with an Ostwald viscometer. [ Evaluation Example 5 : Evaluation of Haze]

The films prepared above were each immersed in a 1% NaOH aqueous solution at 85°C for 15 minutes. A haze meter (model name: SEP-H) of Nihon Semitsu Kogaku (Japan) was used to measure the haze before and after immersion using a C light source. [table 5] Transverse heat shrinkage rate (80℃) Transverse heat shrinkage rate (90℃) Tc (℃) Tm (℃) Heat of crystallization (J/g) Agglutination (%) Intrinsic viscosity (dl/g) Ex. 1-1 58% 70% - 199 - 0.02 0.76 Ex. 1-2 65% 78% - 171 - 1.3 0.78 Ex. 1-3 62% 79% 90 171 0.3 0.5 0.79 Ex. 1-4 67% 79% 78 - 1.2 0 0.76 C. Ex. 1-1 68% 78% 82 166 0.1 9.7 0.76 [Table 6] Transverse heat shrinkage rate (80℃) Transverse heat shrinkage rate (90℃) Tc (℃) Tm (℃) Heat of crystallization (J/g) Agglutination (%) Intrinsic viscosity (dl/g) Ex. 2-1 58% 70% - 199 - 0.02 0.76 Ex. 2-2 63% 72% - 178 - 0.15 0.80 Ex. 2-3 65% 78% - 171 0.3 1.3 0.78 Ex. 2-4 66% 79% - 172 1.2 4.0 0.79 C. Ex. 2-1 68% 78% 82 166 0.1 9.7 0.76 [Table 7] Transverse heat shrinkage rate (80℃) Transverse heat shrinkage rate (90℃) Haze (%) Tc (℃) Tm (℃) Agglutination (%) Intrinsic viscosity (dl/g) forward Rear Ex. 3-1 40% 60% 5 5 - 200 0.2 0.61 Ex. 3-2 45% 66% 5 5 - 180 0.5 0.62 Ex. 3-3 43% 63% 5 41 80 150 0.8 0.59 Ex. 3-4 49% 69% 6 40 79 150 1 0.57 Ex. 3-5 44% 65% 4 4 - 176 2 0.69 C. Ex. 3-1 50% 70% 3 3 - 165 10 0.71

As shown in Tables 5 to 7, the polyester film prepared in the examples and the recycled polyester chip prepared by the method for regenerating a polyester container using the polyester film each have a low agglomeration fraction and are resistant to heat of crystallization and inherent The viscosity characteristics are all excellent. [Table 8] Transverse heat shrinkage rate (100℃) Tc (℃) Tm (℃) Heat of crystallization (J/g) Agglutination (%) Intrinsic viscosity (dl/g) Ex. 4-1 78% - 165 - 8 0.68 Ex. 4-2 78% - 170 - 6 0.80 Ex. 4-3 60% - 165 - 5 0.68 Ex. 4-4 50% - 170 - 3 0.80 Ex. 4-5 75% - 165 - 4 0.69 Ex. 4-6 76% - 170 - 4 0.79 Ex. 4-7 55% - 165 - 2 0.75 Ex. 4-8 45% - 170 - 1 0.86 C. Ex. 4-1 78% - 165 - 10 0.68 C. Ex. 4-2 79% - 170 - 8 0.68

As shown in Table 8, the polyester film prepared in the examples and the recycled polyester chip prepared by the method for regenerating a polyester container using the polyester film each have a low agglomeration fraction.

(1), (2), (3): steps

Figure 1 schematically depicts a method of regenerating a polyester container according to a specific example.

Fig. 2 shows the heat shrinkage rates of the polyester films of Examples 1-1 to 1-4 and Comparative Example 1-1.

(1), (2), (3): steps

Claims (10)

A polyester film comprising a copolyester resin containing a diol component and a dicarboxylic acid component, and The polyester film has a heat shrinkage rate of 30% or more in the main shrinkage direction after heat treatment at a temperature of 80°C for 10 seconds, and It is a melting point of 170°C or higher as measured by differential scanning calorimetry. A polyester film comprising a copolyester resin containing a diol component and a dicarboxylic acid component, the polyester film and having a value of 50% or more when immersed in a 1% NaOH aqueous solution for 15 minutes Low haze. The polyester film of claim 1 or 2, wherein the glycol component is at least one selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, and cyclohexanedi Methanol. The polyester film of claim 1 or 2, wherein, based on the total moles of the diol component, the copolyester resin contains ethylene glycol in an amount of 55 to 94 mole% and 1 to 20 mole% Servings of diethylene glycol. The polyester film of claim 1 or 2, wherein the copolyester resin contains neopentyl glycol in an amount of 5 to 35 mol% based on the total moles of the diol component. The polyester film of claim 1 or 2, wherein the crystallization temperature of the polyester film is not measured by differential scanning calorimetry or is 70°C to 95°C, and The heat of crystallization of the polyester film at the crystallization temperature is not measured or is 0.01 to 50 J/g. The polyester film of claim 1 or 2, wherein the glass transition temperature (Tg) of the polyester film is 60° C. or higher as measured by differential scanning calorimetry. Such as the polyester film of claim 1 or 2, which has a heat shrinkage rate of 30% or more in a first direction after heat treatment at a temperature of 100°C for 10 seconds, After heat treatment at a temperature of 90°C for 10 seconds, a heat shrinkage rate of 50% or higher in the first direction, and After heat treatment at a temperature of 70° C. for 10 seconds, a thermal shrinkage rate of 5% to 55% in the first direction. Such as the polyester film of claim 1 or 2, wherein within the temperature range of 0.35 × Tm°C to 0.40 × Tm°C, the increase rate of heat shrinkage in a first direction is 2.5%/°C to 4.0%/°C, as well as In the temperature range of 0.45 × Tm°C to 0.50 × Tm°C, the increase rate of the heat shrinkage rate in the first direction is 0.1%/°C to 1.0%/°C. The polyester film of claim 1 or 2, wherein when several small pieces obtained by breaking a polyethylene terephthalate (PET) container provided with the polyester film are heat-treated at a temperature of 200°C to 220°C From 60 minutes to 120 minutes, the agglutination fraction is 8% or less.

Images