KR102349923B1 - Polyester film, preparation method thereof and method for reproducing polyethyleneterephthalate container using same - Google Patents

Abstract

The embodiment relates to a polyester film, a method for manufacturing the same, and a method for recycling a polyethylene terephthalate (PET) container using the same, wherein the polyester film has excellent seaming properties and recyclability because crystallinity is controlled and thus, in the regeneration process Clumping hardly occurs even when heat treated for a long time.

Description

Polyester film, manufacturing method thereof, and recycling method of polyethylene terephthalate container using the same

The embodiment relates to a polyester film, a method for manufacturing the same, and a method for recycling a polyethylene terephthalate container using the same. Specifically, the embodiment relates to a polyester film excellent in seaming properties and recyclability by controlling crystallinity, a method for producing the same, and a method for regenerating a polyethylene terephthalate (PET) container equipped with the polyester film.

Recently, heat-shrinkable labels and packaging materials are attracting attention as more and more cases of beverage or food containers are manufactured in various forms or front packaging is applied to induce consumers' attention. Such heat-shrinkable labels and packaging materials use the characteristic of a polymer film being stretched and oriented and then shrunk to a shape before stretching again at a specific temperature or higher. In a general heat-shrinkable labeling or packaging process, a heat-shrinkable film is cut, printed in a desired design, rolled up and both ends are adhered with an adhesive solvent, then loosely covered on a container and shrunk by applying heat.

The film applied to the heat shrink process requires not only basic properties such as heat resistance, chemical resistance, weather resistance, printability, etc., but also container sealing property, heat shrink uniformity, running characteristics in the longitudinal direction, and crack resistance. Conventionally, polyvinyl chloride film, polystyrene film, polypropylene film, etc. have been used in this heat-shrinkage process, and in recent years, polyester films with characteristics such as high heat resistance and weather resistance, ease of incineration, and excellent printability are widely used. .

However, since the normal polyester film has a fast shrinkage rate and a high shrinkage stress, defects due to non-uniform shrinkage or crushing of plastic containers have occurred. Accordingly, Korean Patent Application Laid-Open No. 2002-0062838 discloses that 5 wt% or more of polyester elastomer is blended in a heat-shrinkable polyester film to suppress the occurrence of wrinkles, shrinkage stains, distortion, etc. due to heat shrinkage during full packaging of plastic bottles. is starting

As such, the polyester film used in the heat shrinking process is manufactured by lowering the crystallinity by blending a soft component with the polyester resin, and thermal properties such as shrinkage rate and shrinkage stress by temperature and chemical resistance suitable for the seaming process; And it is being developed to have recyclability, which has recently been highlighted as a waste plastic problem.

In addition, as concerns about environmental problems increase in recent years, a response to the recycling problem of products manufactured using a thermoplastic polymer is required. In particular, polyethylene terephthalate (PET), a thermoplastic resin with excellent properties such as heat resistance, processability, transparency and non-toxicity, is widely used to manufacture a wide range of products such as films, fibers, bottles, containers, etc. is going on

Korean Patent Publication No. 2002-0062838

Accordingly, the embodiment is a polyester film in which crystallinity is controlled so that it has excellent seaming properties and excellent recyclability, so that irregularly aggregated clumping hardly occurs even when heat-treated for a long time in the regeneration process, a method for producing the same; And to provide a method of recycling a polyethylene terephthalate container using the same.

The polyester film according to one embodiment includes a copolymerized polyester resin in which diol and dicarboxylic acid are copolymerized, and optionally includes a homo polyethylene terephthalate (HOMO-PET) resin, and is measured by differential scanning calorimetry. The measured melting point (Tm) is 190°C to 230°C, the clumping ratio is 10% or less, and the peeling force is 150 gf/3 cm or more.

A method for producing a polyester film according to another embodiment comprises the steps of: preparing a copolymerized polyester resin in which diol and dicarboxylic acid are copolymerized; Preparing an unstretched sheet by selectively adding a homo polyethylene terephthalate (HOMO-PET) resin to the co-polyester resin, and melt-extruding the co-polyester resin at a temperature of 250° C. to 300° C.; And after stretching the unstretched sheet, comprising the step of heat-setting at a temperature of 70 ℃ to 100 ℃ to prepare a polyester film, the polyester film melting point (Tm) measured by differential scanning calorimetry (Differential Scanning Calorimetry) ) is 190 ° C. to 230 ° C., the clumping ratio of the polyester film is 10% or less, and the peeling force is 150 gf / 3 cm or more.

A method for regenerating a polyethylene terephthalate container according to another embodiment includes the steps of preparing a polyethylene terephthalate (PET) container equipped with the polyester film; pulverizing a polyethylene terephthalate (PET) container equipped with the film to obtain flakes; and manufacturing a recycled polyester chip by heat-treating the flakes, wherein a clumping ratio of the flakes is 10% or less, and the flakes are obtained by pulverizing the polyethylene terephthalate (PET) container. 1 flake and the 2nd flake obtained by grind|pulverizing the said polyester film is included.

The polyester film according to the embodiment has a melting point (Tm) measured by a differential scanning calorimeter that satisfies 190°C to 230°C, and has a peeling force of 150 gf/3 cm or more, so that crystallinity can be easily controlled. Thermal and chemical properties were improved. Therefore, the polyester film according to the embodiment not only has excellent shrinkage by temperature, but also has excellent adhesion by solvent even when applied to gravure printing, UV curing printing, variable sleeve offset printing (VSOP), etc. suitable for

In addition, the polyester film has a low defect rate according to the recycling process because the occurrence of clumping is suppressed even in the heat treatment process for a long time. Therefore, it is possible to improve the quality, yield, and productivity of the recycled polyester chip manufactured through the recycling method of the polyethylene terephthalate container using the polyester film.

Moreover, since the method for regenerating the polyethylene terephthalate container according to the embodiment does not require a separate process for separating the container and the film, it is economical by reducing time and cost.

1 shows before and after heat shrinkage of a polyester film applied to a product.
2 shows a method for measuring the clumping of a polyethylene terephthalate container equipped with a polyester film.
Figure 3 shows a method for measuring the peel force of the polyester film.
Figure 4 shows a method for measuring the thermal shrinkage of the polyester film.
5 shows a differential scanning calorimetry (DSC) curve of the polyester film of Examples 1-3.

Hereinafter, the invention will be described in detail through embodiments. The embodiments are not limited to the contents disclosed below and may be modified in various forms as long as the gist of the invention is not changed.

In the present specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

It should be understood that all numbers and expressions indicating amounts of ingredients, reaction conditions, etc. described in this specification are modified by the term "about" in all cases unless otherwise specified.

In this specification, terms such as first, second, primary, secondary, etc. are used to describe various components, and the components are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

Although heat-shrinkable labels or packaging materials made of polyester film have excellent thermal properties and chemical resistance, they are difficult to recycle, so most of them are discarded after use. This is because, when the polyester film is put into the current recycling process, that is, the recycling process, the polyester film causes various process defects in high-temperature heat treatment for a long time, resulting in low recyclability. Accordingly, an additional process may be performed to improve recyclability, but there is a problem in that the process cost increases.

In addition, a method of controlling the components of the polyester film may be used to improve recyclability, but in this case, due to the high crystallinity of the polyester film, when applied to gravure printing, UV curing printing, variable sleeve offset printing (VSOP), etc. It was not suitable for the heat shrink process and seaming process because of the low adhesion.

However, the polyester film according to the embodiment has excellent thermal properties and chemical resistance, so it is suitable for a heat shrink process and a seaming process, so it is easy to apply as various types of heat shrinkable labels and packaging materials, and also has excellent recyclability after use is completed.

In addition, polyethylene terephthalate (PET) containers recovered from general consumers are labeled with product information. Conventionally, after washing and pulverizing them, to remove a large amount of film contained in the pulverized product, liquid specific gravity separation, Recycled polyester chips have been manufactured by performing additional processes such as pelletizing after dehydration drying and/or wind specific gravity separation. However, even after the above process, it is difficult to completely remove the film used as the label of the polyethylene terephthalate (PET) container, and there is a problem in that the recycled polyester chip is colored due to the ink contained in the film. In addition, due to the thermal properties of the film, there is a problem in that the regenerated polyester chips are irregularly aggregated and clumping occurs in the regeneration process, particularly in the heat treatment process.

Accordingly, a specific gravity separation method using a film of low specific gravity polymer such as polystyrene, polyethylene, or polypropylene as a label has been proposed so that specific gravity separation can be easily achieved. However, the low specific gravity is not effectively achieved due to the ink layer, so it is still difficult to completely separate and remove the film, and the problem of the residual ink coloring the recycled polyester chips could not be solved.

The polyester film according to the embodiment has excellent recyclability while having excellent shrinkage characteristics and seaming characteristics in various printing methods because crystallinity is controlled, so that clumping hardly occurs even during long-time heat treatment in the regeneration process. Therefore, it is possible to improve the quality, yield and productivity of the recycled polyester chip manufactured through the recycling method of the polyethylene terephthalate (PET) container including the polyester film. In addition, the polyester film according to the embodiment may be usefully applied as a heat-shrinkable label or packaging material to containers of various types of products including beverages and food.

polyester film

The polyester film according to one embodiment includes a copolymerized polyester resin in which diol and dicarboxylic acid are copolymerized, and optionally includes a homo polyethylene terephthalate (HOMO-PET) resin, and is measured by differential scanning calorimetry. The measured melting point (Tm) is 190°C to 230°C, the clumping ratio is 10% or less, and the peeling force is 150 gf/3 cm or more.

The melting point (Tm) of the polyester film according to the embodiment measured by Differential Scanning Calorimetry may be 190°C to 230°C. For example, the melting point of the film measured by differential scanning calorimetry is 193°C to 230°C, 195°C to 228°C, or 195°C to 225°C.

By adjusting the melting point of the polyester film to the above range, the crystallinity of the polyester film is effectively controlled, so that the film or polyethylene terephthalate (PET) container containing the film is recycled while having excellent seaming properties, which is adhesion by a solvent. The clumping fraction during the process is very low, so it is possible to improve recyclability while preventing environmental pollution.

Specifically, when the melting point of the polyester film exceeds the above range, the adhesive strength by the solvent of the polyester film may be reduced and it may be difficult to use in the seaming process, and if the melting point is less than the above range, the clumping fraction may increase have.

The differential scanning calorimeter (DSC) may specifically be a modulated differential scanning calorimeter (modulated DSC, MDSC), and more specifically, a temperature-modulated differential scanning calorimeter (temperature-modulated DSC, TMDSC).

In addition, the enthalpy of melting (ΔHm) measured by differential scanning calorimetry (Differential Scanning Calorimetry) of the polyester film according to the embodiment may be 12 J/g or more. For example, the enthalpy of melting measured by differential scanning calorimetry of the film may be 12 J/g or more or 15 J/g or more, 12 J/g to 30 J/g, 12 J/g to 28 J/g, 15 J/g to 33 J/g, 12 J/g to 30 J/g or 15 J/g to 28 J/g.

By adjusting the enthalpy of melting of the polyester film to the above range, the crystallinity of the polyester film is effectively controlled so that the film or polyethylene terephthalate (PET) container containing the film is excellent in seaming properties, which is adhesion by a solvent. During the regeneration process, the clumping fraction is very low, thereby preventing environmental pollution and improving recyclability.

Specifically, when the melting enthalpy of the polyester film is less than the above range, the thermal properties are not good, and thus, the clumping fraction may be increased in the recycling process for recycling. In addition, when the melting enthalpy of the polyester film exceeds the above range, the lumping fraction may be lowered, but peeling force may be lowered, and thus it may be difficult to use as a heat shrinkable film.

Specifically, the melting enthalpy may be measured by scanning using a differential scanning calorimeter (DSC) mode at a temperature increase rate of 10 °C/min. There More specifically, the melting enthalpy with a differential scanning calorimeter (DSC) can be measured by the first scanning (1 ^st scan) or the second scan (2 ^nd scan), the melting enthalpy in the present specification is a DSC Thus, it was measured by first scanning the polyester film.

A glass transition temperature (Tg, Glass Transition Temperature), a crystallization temperature (Tc, Crystallization Temperature), and a melting point (Tm, Meting Temperature) can be confirmed from a heat flow curve obtained by scanning.

Specifically, in the heat flow curve obtained by scanning, the first endothermic temperature is the glass transition temperature (Tg), the exothermic temperature measured after the glass transition temperature (Tg) is the crystallization temperature (Tc), and after the crystallization temperature (Tc) The endothermic temperature measured at is the melting point (Tm).

At this time, the integral value at the melting point (Tm) was calculated as the melting enthalpy. Specifically, the melting enthalpy is the energy in the section where endotherm occurs in the heat flow curve of the differential scanning calorimeter, and the trend line from the melting start temperature to the complete melting temperature is set as the baseline, and the integral value of the peak according to the baseline is converted was calculated.

5 shows a differential scanning calorimetry (DSC) curve of the polyester film of Examples 1-3. Specifically, referring to FIG. 5 , the first endothermic temperature of 73.34° C. is the glass transition temperature, the exothermic temperature measured after the glass transition temperature of 100.59° C. is the crystallization temperature, and the endothermic temperature measured after the crystallization temperature is 201.99° C. is the melting point. At this time, the integral value at the melting point of 25.94 J/g is the melting enthalpy. More specifically, the trend line TL from the melting start temperature (T1) to the complete melting temperature (T2) was set as the baseline, and the integral value of the peak along the baseline was calculated as the melting enthalpy.

The glass transition temperature (Tg) of the polyester film measured by a differential scanning calorimeter may be 60 ℃ or more. For example, the glass transition temperature (Tg) of the film measured with a differential scanning calorimeter may be 60°C or higher, 65°C or higher, or 70°C or higher, and 60°C to 85°C, 60°C to 80°C, or 60°C to 78°C. °C.

In addition, the crystallization temperature (Tc) of the polyester film measured with a differential scanning calorimeter may not be measured, or may be 70°C to 130°C. For example, the crystallization temperature (Tc) measured by differential scanning calorimetry of the film is not measured, or is 80°C to 130°C, 85°C to 125°C, 90°C to 125°C, 96°C to 125°C or 98°C to It may be 120°C. By adjusting the crystallization temperature of the polyester film to the above range, the crystallinity of the polyester film is effectively controlled, so that the clumping fraction is very low during the regeneration process of the film or a polyethylene terephthalate (PET) container containing the film. Recyclability can be improved while preventing pollution.

The amount of heat of crystallization of the film measured at the crystallization temperature (Tc) may be 0.01 J/g to 50 J/g. For example, the heat of crystallization may be calculated as an integral value at the crystallization temperature, and the heat of crystallization of the film at the crystallization temperature is 0.01 J/g to 40 J/g, 0.05 J/g to 30 J/g , 0.1 J/g to 20 J/g, 0.1 J/g to 10 J/g, 0.2 J/g to 10 J/g, 0.3 J/g to 10 J/g or 0.5 J/g to 9 J/g can be As the amount of heat of crystallization of the polyester film satisfies the above range, the crystallinity of the polyester film is effectively controlled so that the clumping fraction is very low during the regeneration process of the film or a polyethylene terephthalate (PET) container containing the film. Recyclability can be improved while preventing pollution.

In addition, the lumping fraction of the polyester film is 10% or less. For example, when a pressure of 8.7 kPa is applied to the pulverized flakes of the polyethylene terephthalate (PET) container equipped with the polyester film, and heat-treated at a temperature of 210 ° C. for 90 minutes, the lumping fraction is 9% or less, 8.5% or less, 8% or less, 6% or less, 5% or less, 4% or less, preferably 3% or less, 2% or less, 1.5% or less, 1% or less, 0.8% or less, 0.5% or less .

The clumping refers to aggregates that may be formed during the regeneration process, and the size of the aggregates may be, for example, three times or more of the size of the flake particles before the heat treatment. The lumping fraction refers to the weight ratio of the aggregates based on the total weight of the first mixed flakes, that is, the flakes before the heat treatment, and may be calculated according to Equation 1 below.

[Equation 1]

Specifically, during the regeneration process of a polyethylene terephthalate (PET) container equipped with a film label, the pulverized flakes are passed through a sieve and then subjected to a heat treatment process. At this time, the pulverized flakes may form agglomerates while agglomerated with each other, and such agglomerates are referred to as clumping. The agglomerates are separated again through a sieve, and the weight is measured, and the weight ratio of the agglomerates is calculated based on the total weight of the flakes before the heat treatment, so that the lumping fraction can be obtained. Therefore, the higher the value of this clumping fraction, the lower the recyclability.

The polyester film according to the embodiment does not cause wrinkles or dents of the polyethylene terephthalate container when applied as a label for a polyethylene terephthalate (PET) container because crystallinity is effectively controlled. In addition, even when the pulverized flakes are heat-treated together with the polyethylene terephthalate container during the regeneration process after completion of use, the clumping fraction is very low, so recyclability can be improved, as well as the quality and yield of recycled polyester chips manufactured by recycling and productivity.

In the recycling process, when flakes are fused to form clumping, it can cause various problems, so the American Association of Plastic Recyclers (APR) has prepared a procedure (APR PET-S-08) to evaluate the clumping fraction (%). have. Specifically, the lumping fraction is pulverized to 3 parts by weight of the polyester film and 97 parts by weight of a polyethylene terephthalate container to a particle diameter of 9.5 mm or less, and a pressure of 8.7 kPa (applied to a cylinder having a diameter of 6 cm at a temperature of 210 ° C. After heat treatment for 90 minutes under a load of 2.5 kgf), there may be a rate that cannot pass through a sieve (0.625" sieve) with a hole size of 11.2 mm.

In addition, the polyester film according to the embodiment may have excellent adhesion by a solvent, that is, a seaming property.

Specifically, the peeling force of the polyester film according to the embodiment may be 150 gf / 3 cm or more. For example, the peel force may be 150 gf/3 cm or more, 180 gf/3 cm or more, 200 gf/3 cm or more, 230 gf/3 cm or more, 250 gf/3 cm or more, 300 gf/3 cm or more, or 330 gf/3 cm or more, 150 gf/3 cm to 3000 gf/3 cm, 180 gf/3 cm to 2800 gf/3 cm, 200 gf/3 cm to 2500 gf/3 cm, 250 gf/3 cm to 2000 gf/3 cm, 300 gf/3 cm to 3000 gf/3 cm, 300 gf/3 cm to 2500 gf/3 cm, 300 gf/3 cm to 2000 gf/3 cm, 330 gf/3 cm to 1500 gf/3 cm or 330 gf/3 cm to 1300 gf/3 cm. By adjusting the peeling force to the above range, the seaming property, which is the adhesive force of the polyester film by the solvent, is excellent, and thus it is suitable for use in the seaming process.

The peel force may be measured using the two polyester films (a first polyester film and a second polyester film). Specifically, 1,3-dioxolane is applied to one side of the first polyester film in the form of a band having a width of 2 mm and a length of 30 mm to form an adhesive portion, and a second poly The ester film was laminated. At this time, while applying 1,3-dioxolane, the second polyester film was immediately laminated. After aging by applying a pressure of 160 Pa to the bonding portion for 1 hour, the maximum force measured when the first and second polyester films were peeled off at a speed of 300 mm/min and an angle of 180° was the peeling force was measured.

In addition, in the polyester film according to the embodiment, the shrinkage rate in the main shrinkage direction for each temperature may be adjusted within a specific range. For example, when the polyester film is heat-treated at a temperature of X°C for 10 seconds, when the shrinkage in the main shrinkage direction is defined _{as T X , the ranges of T 70} , T ₈₀ , T ₉₀ and T ₁₀₀ can be adjusted. . The heat treatment for obtaining the T _X may be specifically immersing the polyester film in hot water at X° C. for 10 seconds.

Specifically, when the film is heat-treated at a temperature of 70° C. for 10 seconds, the thermal contraction rate (T ₇₀ ) in the first direction may be 0% to 50%. For example, T ₇₀ can be between 0.1% and 50%, between 0.5% and 48%, between 0.5% and 46%, between 2% and 46%, or between 3.5% and 45.5%.

In the present specification, the first direction may be a transverse direction (TD) or a longitudinal direction (MD), and the second direction perpendicular to the first direction may be a longitudinal direction (MD) or a transverse direction (TD). . Specifically, the first direction may be the lateral direction (TD) as the main contraction direction, and the second direction may be the longitudinal direction (MD).

In addition, when the film is heat-treated at a temperature of 80° C. for 10 seconds, the thermal contraction rate (T ₈₀ ) in the first direction may be 20% or more. For example, T ₈₀ may be 23% or more, 25% or more, 40% or more, 45% or more, 50% or more, or 55% or more, 20% to 85%, 23% to 80%, 25% to 75% and 40% to 85%, 45% to 80%, 50% to 78%, or 55% to 75%.

When the film is heat-treated at a temperature of 90° C. for 10 seconds, the thermal contraction rate (T ₉₀ ) in the first direction may be 40% or more. For example, T ₉₀ may be 50% or more, 60% or more, or 70% or more, and may be 40% to 85%, 50% to 80%, 60% to 78%, or 70% to 80%.

In addition, when the film is heat-treated at a temperature of 100° C. for 10 seconds, the thermal contraction rate (T ₁₀₀ ) in the first direction may be 45% to 85%. For example, T ₁₀₀ can be between 45% and 80%, between 50% and 80%, between 65% and 80%, between 70% and 80%, between 70% and 78% or between 73% and 78%. When heat treatment at a temperature of 80° C. for 10 seconds, the thermal contraction rate in the first direction satisfies the above range, so that it is easy to perform a labeling process in which the film surrounds at least a portion of the container. Specifically, when the film is applied as a label for a polyethylene terephthalate (PET) container, wrinkles or distortion of the polyethylene terephthalate container do not occur.

On the other hand, in the polyester film according to the embodiment, the shrinkage rate for each temperature in the first direction and the second direction perpendicular to the first direction may be adjusted within a specific range. For example, when the polyester film is heat-treated at a temperature of X° C. for 10 seconds, when the shrinkage in the second direction _{is defined as T X} ', T ₇₀ ', T ₇₅ ', T ₈₀ ', T ₉₀ ' and T _{A range of 100} ' can be adjusted within a specific range. The heat treatment for obtaining the T _X ' may be immersing the polyester film in hot water at X°C for 10 seconds.

_{T 70} ', T ₇₅ ', T ₈₀ ', T ₉₀ ' and T ₁₀₀ ' of the polyester film may each independently be -10% to 10%. For example, T ₇₀ ', T ₇₅ ', T ₈₀ ', T ₉₀ ' and T ₁₀₀ ' of the polyester film are each -10% or more, -8% or more, -6% or more, -4% or more, -2% or more or 0% or more, and 10% or less, 8% or less, 6% or less, 4% or less, or 2% or less.

Specifically, when the film is heat-treated at a temperature of 100° C. for 10 seconds, the thermal contraction rate (T ₁₀₀ ′) in the second direction perpendicular to the first direction may be 7% or less. For example, the T ₁₀₀ ' may be 7% or less or 6% or less, -16% to 7%, -10% to 7% -7% to 7%, -5% to 7%, 0% to 7 %, 0.5% to 7% or 2% to 6%.

In addition, the polyester film may have a light transmittance of 90% or more at a wavelength of 550 nm. Specifically, the light transmittance measured at a wavelength of 550 nm of the film before and after immersion in a 1% concentration of sodium hydroxide (NaOH) aqueous solution at a temperature of 85° C. is 90.5% or more, 91% or more, 92% or more, or 93% or more, respectively. can

The amount of change in light transmittance before and after immersing the polyester film in an aqueous solution of sodium hydroxide (NaOH) having a concentration of 1% at a temperature of 85° C. may be 0.7% or less. For example, the amount of change in the light transmittance of the film before and after the immersion may be 0.6% or less or 0.5% or less.

The amount of change in the light transmittance means the absolute value of the difference between the light transmittance of the film measured at a wavelength of 550 nm before the immersion and the light transmittance of the film measured at a wavelength of 550 nm after the immersion.

In addition, the amount of change (ΔL) of Col-L before and after immersing the film in a 1% concentration of sodium hydroxide (NaOH) aqueous solution at a temperature of 85° C. may be 0.7 or less, and the amount of change of Col-a (Δa) is 0.5 or less, and the amount of change (Δb) of Col-b may be 0.5 or less. For example, the amount of change (ΔL) of Col-L before and after the immersion may be 0.65 or less, 0.6 or less, 0.55 or less, or 0.5 or less, and the change amount (Δa) of Col-a is 0.3 or less, 0.1 or less, 0.08 or less , 0.06 or less, or 0.05 or less, and the amount of change (Δb) of Col-b may be 0.3 or less, 0.1 or less, 0.08 or less, or 0.07 or less.

The amount of change in Col-L (ΔL) means the absolute value of the difference between the Col-L value before immersion and the Col-L value after immersion, and the amount of change in Col-a (Δa) is the Col-L value before immersion. means the absolute value of the difference between the -a value and the Col-a value after the immersion, and the amount of change (Δb) of the Col-b is the absolute difference between the Col-a value before the immersion and the Col-a value after the immersion means value.

The Col-L, the Col-a, and the Col-b are color systems established by the Commission International d'Eclairage (CIE), and Color is L (brightness), a (green to red). Complementary color), b (complementary color from yellow to blue) to express color, and can be measured using UltraScan PRO (manufacturer: Hunterlab), but is not limited thereto.

The polyester film according to the embodiment includes a copolymerized polyester resin. Specifically, the copolymerized polyester resin may be a polymerization of two or more types of diols and dicarboxylic acids, and more specifically, may be a copolymerized polyethylene terephthalate (Co-PET) resin.

Specifically, the diol is ethylene glycol, diethylene glycol, neopentyl glycol, propanediol substituted or unsubstituted with an alkyl group, butanediol substituted or unsubstituted with an alkyl group, pentanediol substituted or unsubstituted with an alkyl group, substituted with an alkyl group, or It may include at least one selected from the group consisting of unsubstituted hexanediol, octanediol substituted or unsubstituted with an alkyl group, and combinations thereof.

For example, the diol is ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,2-octanediol, 1,3-octanediol, 2,3-butanediol, 1,3-butanediol , 1,4-butanediol, 1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl- It may include at least one selected from the group consisting of 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,1-dimethyl-1,5-pentanediol.

The dicarboxylic acid may include an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, an alicyclic dicarboxylic acid, or an ester thereof.

For example, the dicarboxylic acid may be terephthalic acid, dimethylterephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, orthophthalic acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, an ester thereof, or a combination thereof. can Specifically, the dicarboxylic acid may include at least one selected from the group consisting of terephthalic acid, dimethyl terephthalate, naphthalenedicarboxylic acid, and orthophthalic acid.

According to one embodiment, the copolymer polyester resin may be a polymerization of two or more kinds of diols and aromatic dicarboxylic acids. Specifically, the copolymerized polyester resin may be a polymer obtained by polymerizing a diol including ethylene glycol and one or more comonomers, and an aromatic dicarboxylic acid.

The diol may include ethylene glycol and at least one comonomer selected from the group consisting of neopentyl glycol and diethylene glycol.

Specifically, the polyester film may contain 50 mol% to 90 mol% of ethylene glycol. For example, the polyester film may contain ethylene glycol in an amount of 60 mol% to 90 mol%, 65 mol% to 88 mol%, 68 mol% to 85 mol%, or 70 mol% to 83 mol%.

In addition, the polyester film may contain at least 10 mol% of one or more comonomers selected from the group consisting of neopentyl glycol and diethylene glycol. For example, the polyester film may contain 10 mol% or more, 13 mol% or more, or 15 mol% or more of at least one comonomer selected from the group consisting of neopentyl glycol and diethylene glycol, and 10 mol% to 30 mol%, 10 mol% to 29 mol%, 10 mol% to 28 mol%, 15 mol% to 30 mol%, 15 mol% to 29 mol%, 15 mol% to 28 mol%. When the content of the comonomer satisfies the above range, it is possible to more effectively control crystallinity while having excellent thermal shrinkage in the main shrinkage direction.

In addition, when the content of the comonomer is less than the above range, the heat shrinkage property of the polyester film may be reduced. Specifically, the rate of thermal contraction with respect to the main shrinkage direction of the polyester film may not be sufficient at a specific temperature, and the heat shrinkage rate in a direction perpendicular to the main shrinkage direction of the polyester film may be excessively high at a specific temperature.

Specifically, the polyester film may include diethylene glycol as a comonomer. For example, the content of diethylene glycol is 1 mol% to 10 mol%, 1 mol% to 8 mol%, 3 mol% to 6 mol%, 3.5 mol% to 5.5 mol% or 3.8 mol% to 5.2% can

In addition, the polyester film may include neopentyl glycol as a comonomer. For example, the content of neopentyl glycol is 5 mol% to 35 mol%, 7 mol% to 33 mol%, 10 mol% to 30 mol%, 13 mol% to 28 mol%, or 15 mol% to 25 mol% can be

When the content of neopentyl glycol satisfies the above range, the rate of heat shrinkage in the first direction or in the second direction perpendicular to the first direction during heat shrinkage of the polyester film is easily controlled, so that wrinkles occur when the film is applied to a container or It is possible to more effectively prevent deformation from occurring.

In addition, the polyester film may include both diethylene glycol and neopentyl glycol as a comonomer. When the polyester film includes diethylene glycol and neopentyl glycol as comonomers, the molar ratio of the neopentyl glycol to the diethylene glycol is 1: 3 to 6, 1: 3 to 5, or 1: 3 to 4 can be

In addition, the polyester film may further include a monohydric alcohol in addition to the diol component. For example, the monohydric alcohol may be methanol, ethanol, isopropyl alcohol, allyl alcohol, or benzyl alcohol. Specifically, the polyester film may further include 10 mol% to 30 mol%, 13 mol% to 25 mol%, or 15 mol% to 22 mol% of monohydric alcohol, but is not limited thereto.

The dicarboxylic acid may include an aromatic dicarboxylic acid. For example, the polyester film may include 80 mol% or more, 90 mol% or more, 95 mol% or more, 99 mol% or more, or 100 mol% of terephthalic acid or dimethyl terephthalic acid.

The co-polyester resin may be formed by polymerization of diol and dicarboxylic acid through transesterification.

Specifically, one or more catalysts selected from the group consisting of manganese acetate tetrahydrate, calcium, and zinc may be used as a catalyst for the transesterification reaction. The content of the catalyst may be 0.02 parts by weight to 0.2 parts by weight, 0.02 parts by weight to 0.1 parts by weight, or 0.05 parts by weight to 0.1 parts by weight based on the total weight of the dicarboxylic acid.

In addition, after the transesterification reaction is completed, at least one additive selected from the group consisting of silica, potassium and magnesium; stabilizers such as trimethylphosphate; and a polymerization catalyst such as antimony trioxide or tetrabutylene titanate may be optionally added.

The polyester film according to the embodiment optionally includes a homo polyethylene terephthalate (HOMO-PET) resin. When the polyester film includes a homo polyethylene terephthalate resin, thermal properties of the film may be improved.

The homo polyethylene terephthalate (HOMO-PET) resin has a polyethylene terephthalate structure in which terephthalic acid (TPA) or dimethylterephthalic acid (DMT) is polymerized with ethylene glycol (EG) is 90% by weight or more, It means a resin included in 95 wt% or more, 97 wt% or more, or 98 wt% or more.

Specifically, the polyester film may contain the homo polyethylene terephthalate resin in an amount of 0.5 wt% to 37 wt%, based on a total of 100 weight of the copolymerized polyester resin and the homo polyethylene terephthalate (HOMO-PET) resin. can For example, the content of the homo polyethylene terephthalate resin may be 0.5 wt % to 37 wt %, 1 wt % to 37 wt % based on a total of 100 weight of the co-polyester resin and the homo polyethylene terephthalate (HOMO-PET) resin wt %, 2 wt % to 37 wt %, 2 wt % to 35 wt %, 2 wt % to 30 wt %, 2 wt % to 27 wt %, 2 wt % to 25 wt %, 2 wt % to 20 wt % , 3 wt% to 37 wt%, 3 wt% to 35 wt%, 3 wt% to 30 wt% or 3 wt% to 25 wt%.

When the content of the homo polyethylene terephthalate resin satisfies the above range, the polyester film is effectively controlled in crystallinity, so that the film or polyethylene terephthalate (PET) container including the film is excellent in seaming properties, which is adhesion by a solvent. The clumping fraction is very low during the regeneration process of

Specifically, when the content of the homo polyethylene terephthalate resin exceeds the above range, the effect of preventing the clumping phenomenon may be improved by improving the thermal characteristics, but the seaming characteristics may be deteriorated.

The polyester film may have a thickness of 10 μm to 100 μm. For example, the thickness of the base layer may be 20 μm to 80 μm, 30 μm to 70 μm, 35 μm to 65 μm, 35 μm to 55 μm, 40 μm to 60 μm, or 35 μm to 45 μm.

Method for producing polyester film

A method for producing a polyester film according to another embodiment comprises the steps of: preparing a copolymerized polyester resin in which diol and dicarboxylic acid are copolymerized; Preparing an unstretched sheet by selectively adding a homo polyethylene terephthalate (HOMO-PET) resin to the co-polyester resin, and melt-extruding the co-polyester resin at a temperature of 250° C. to 300° C.; And after stretching the unstretched sheet, comprising the step of heat-setting at a temperature of 70 ℃ to 100 ℃ to prepare a polyester film, the polyester film melting point (Tm) measured by differential scanning calorimetry (Differential Scanning Calorimetry) ) is 190 ° C. to 230 ° C., the clumping ratio of the polyester film is 10% or less, and the peeling force is 150 gf / 3 cm or more.

The polyester film finally manufactured by the above method controls the composition and process conditions so as to satisfy the aforementioned properties (melting enthalpy, melting point, shrinkage property, etc.). Specifically, in order for the final polyester film to satisfy the characteristics described above, the composition of the co-polyester resin is adjusted, and its extrusion temperature, casting temperature, preheating temperature during stretching, draw ratio for each direction, drawing temperature, drawing speed, etc. Alternatively, the heat treatment temperature and relaxation rate may be adjusted while performing heat treatment and relaxation after stretching.

Hereinafter, each step will be described in more detail.

First, a copolymer polyester resin is prepared. The description of the copolymer polyester resin is the same as described above.

Specifically, the polymerization of the copolymer polyester resin may be carried out through a conventional transesterification reaction and polycondensation reaction, and the diol and dicarboxylic acid components and their contents used in this case are as exemplified above.

Thereafter, a homopolyethylene terephthalate (HOMO-PET) resin is selectively added to the copolymerized polyester resin, and the copolymerized polyester resin is melt-extruded at a temperature of 250° C. to 300° C. to prepare an unstretched sheet.

Specifically, after melt-extruding the copolymer polyester resin or the copolymer polyester resin to which the homo polyethylene terephthalate (HOMO-PET) resin is added at a temperature of 250°C to 300°C or 260°C to 300°C with a T-die , an unstretched sheet can be prepared by cooling. The description of the homo polyethylene terephthalate (HOMO-PET) resin is the same as described above.

chamber while conveying the unstretched sheet at a speed of 10 m/min to 110 m/min, 25 m/min to 90 m/min, 40 m/min to 80 m/min, or 50 m/min to 60 m/min It can be preheated while passing through the

The preheating may be performed at 100° C. to 120° C. for 0.01 minute to 1 minute. For example, the preheating temperature may be 100°C to 120°C or 100°C to 117°C, and the preheating time may be 0.05 minutes to 0.5 minutes or 0.05 minutes to 0.2 minutes.

Thereafter, the preheated unstretched sheet is stretched at a temperature of 70°C to 95°C. For example, the stretching may be performed at 70°C to 95°C, 75°C to 95°C, or 80°C to 90°C.

Specifically, the stretching may be uniaxial stretching or biaxial stretching. More specifically, the stretching may be uniaxial stretching performed in the transverse direction (TD), or may be biaxial stretching performed in the transverse direction (TD) after being performed in the longitudinal direction (MD).

When the stretching is uniaxial stretching, the stretching may be performed at a stretching ratio of 3.5 to 5 times, 3.5 to 4.8 times, or 3.8 to 4.6 times in the transverse direction (TD). In addition, when the stretching is biaxial stretching, the stretching is performed at a stretching ratio of 1.1 to 2 or 1.1 to 1.5 times in the longitudinal direction (MD), and then 3.5 to 5 times, 3.5 in the transverse direction (TD). It may be performed at a draw ratio of times to 4.8 times or 3.8 times to 4.6 times.

In addition, a coating process may be additionally performed after the stretching. Specifically, a coating process may be additionally performed before uniaxial stretching in the transverse direction (TD) or before stretching in the transverse direction (TD) after stretching in the longitudinal direction (MD). More specifically, a coating process for forming an accelerating layer capable of imparting functionality such as antistatic properties to the film may be additionally performed. The coating process may be performed by spin coating or in-line coating, but is not limited thereto.

Thereafter, the stretched sheet is heat-set at a temperature of 70° C. to 100° C. to prepare a polyester film.

The heat setting may be annealing, and may be performed at a temperature of 70° C. to 100° C. or 70° C. to 95° C. for 0.01 minutes to 1 minute or 0.05 minutes to 0.5 minutes.

Regeneration method of polyethylene terephthalate container

A method for regenerating a polyethylene terephthalate container according to another embodiment includes the steps of preparing a polyethylene terephthalate (PET) container equipped with the polyester film; pulverizing a polyethylene terephthalate (PET) container equipped with the film to obtain flakes; and manufacturing a recycled polyester chip by heat-treating the flakes, wherein a clumping ratio of the flakes is 10% or less, and the flakes are obtained by pulverizing the polyethylene terephthalate (PET) container. 1 flake and the 2nd flake obtained by grind|pulverizing the said polyester film is included.

In order to regenerate a polyethylene terephthalate (PET) container according to an embodiment, first, a polyethylene terephthalate (PET) container in which the polyester film surrounds at least a part is prepared .

Conventionally, containers, metals, glass, plastics, etc. are washed to sort the recovered waste products, and the process of removing the film surrounding the container in order to improve the recyclability and quality of the container. performed The removal process has been performed by mechanically tearing or cutting the film, or through an additional process such as liquid specific gravity separation, dehydration drying, wind specific gravity separation, or pelletize.

However, it was difficult to completely remove the film by the removal process, and in particular, it was difficult to improve the quality of the recycled polyester chip manufactured due to the residual ink formed on the film.

The polyester-based container recycling method according to the embodiment can produce a recycled polyester chip without separately performing a process of removing the film surrounding the polyethylene terephthalate (PET) container, thereby reducing costs.

The polyethylene terephthalate (PET) container is provided with the polyester film on the outer surface. Specifically, after surrounding the outer surface of the polyethylene terephthalate container with the polyester film, the film may be contracted by steam or hot air to wrap at least a portion of the outer surface of the polyethylene terephthalate container. For example, the polyester film may be a label of the polyethylene terephthalate container as a heat-shrinkable film, but is not limited thereto.

The description of the polyester film is the same as described above.

Thereafter, a polyethylene terephthalate (PET) container equipped with the film is pulverized to obtain flakes .

Specifically, at least a portion of the outer surface of the polyethylene terephthalate (PET) container is surrounded by the film, and the container and the film are pulverized together to obtain flakes without a separate process for separating the container and the film.

That is, the flakes include a first flake obtained by pulverizing the polyester-based container and a second flake obtained by pulverizing the film.

The particle size of the first flakes may be 0.1 mm to 25 mm, and the particle size of the second flakes may be 0.1 mm to 25 mm. For example, the particle size of the first flake is 0.3 mm to 23 mm, 0.5 mm to 20 mm, 1 mm to 20 mm, 0.5 mm to 15 mm, 0.5 mm to 13 mm, 1 mm to 18 mm, 1 mm and 15 mm to 15 mm, 1 mm to 13 mm or 2 mm to 10 mm, and the particle size of the second flakes is 0.3 mm to 23 mm, 0.5 mm to 20 mm, 1 mm to 20 mm, 0.5 mm to 15 mm. , 0.5 mm to 13 mm, 1 mm to 18 mm, 1 mm to 15 mm, 1 mm to 13 mm, or 2 mm to 10 mm, but is not limited thereto.

Thereafter, the step of washing the pulverized flakes before the heat treatment step may be additionally performed. Specifically, the washing step may be performed with a washing solution comprising water and/or 1 part by weight of an aqueous sodium hydroxide solution at a temperature of 85°C to 90°C.

For example, the pulverized flakes may be first washed with water, second washed with the washing solution, and then washed tertiarily with water. By performing the washing step, impurities that may remain in the pulverized flakes can be removed as well as ink components can be effectively removed, so that the quality and purity of the produced recycled polyester-based chips are improved and recyclability can be maximized.

In addition, after the washing step, drying the washed flakes at 60° C. to 175° C. for 10 minutes to 90 minutes may be additionally performed. For example, the drying step may be performed at 65 °C to 175 °C, 70 °C to 170 °C, 90 °C to 165 °C, 100 °C to 165 °C, 120 °C to 165 °C, 140 °C to 165 °C, or 150 °C to 165 °C. It may be carried out for 10 minutes to 85 minutes, 10 minutes to 70 minutes, 15 minutes to 30 minutes.

The washing and drying steps may be repeated 1 to 5 times. For example, by repeatedly performing the washing and drying steps 2 to 5 times or 3 to 5 times in order, impurities remaining in the flakes can be effectively removed.

Finally, the flakes are heat treated to produce recycled polyester chips .

Specifically, the flakes include a first flake obtained by pulverizing the polyethylene terephthalate (PET) container and a second flake obtained by pulverizing the polyester film.

The heat treatment may 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.

In addition, the clumping ratio of the flakes is 10% or less. Specifically, when a pressure of 8.7 kPa is applied to the flakes and heat treatment is performed at a temperature of 210° C. for 90 minutes, the lumping fraction may be 10% or less. For example, when the flakes are subjected to a pressure of 8.7 kPa and heat treated at a temperature of 210° C. for 90 minutes, the clumping fraction is 9% or less, 8.5% or less, 8% or less, 6% or less, 5% or less, 4 % or less, preferably 3% or less, 2% or less, 1.5% or less, 1% or less, 0.8% or less, 0.5% or less.

Since the clumping fraction that may occur due to the agglomeration of the first flakes and the second flakes is low, the quality of the produced recycled polyester chips is excellent. Specifically, since the flakes include the second flakes obtained by pulverizing the polyester film according to the embodiment, the formation of aggregates is effectively reduced or prevented, thereby improving the quality of the produced recycled polyester chips.

After the heat treatment process, a recycled polyester chip can be obtained. Specifically, after the heat treatment process, it is possible to obtain a recycled polyester chip including the first flakes and the second flakes. For example, the flake may be melt-extruded and then cut to obtain a recycled polyester-based chip, but is not limited thereto.

Recycled Polyester Chips

The recycled polyester chip according to another embodiment is manufactured by the recycling method of the polyethylene terephthalate container.

Specifically, the recycled polyester-based chip may include a first flake including polyethylene terephthalate (PET) and a second flake including a polyester-based resin.

The intrinsic viscosity (IV) of the recycled polyester-based chip may be 0.55 dl/g or more. For example, the intrinsic viscosity of the recycled polyester-based chip may be 0.58 dl/g or more or 0.59 dl/g or more, and 0.55 dl/g to 3.0 dl/g, 0.55 dl/g to 2.0 dl/g, 0.55 dl /g to 1.0 dl/g, 0.58 dl/g to 0.85 dl/g or 0.58 dl/g 0.7 dl/g.

In addition, the recycled polyester chip may include 70 wt% to 99 wt% of polyethylene terephthalate, based on the total weight of the recycled polyester chip, and 1 wt% to 30 wt% of the copolymer polyester resin may include For example, the recycled polyester chip contains 80 wt% to 99 wt%, 90 wt% to 99 wt%, or 95 wt% to 99 wt% polyethylene terephthalate based on the total weight of the recycled polyester chip. and may include 1 wt% to 20 wt%, 1 wt% to 10 wt%, or 1 wt% to 5 wt% of the copolymerized polyester resin.

The above will be described in more detail with reference to the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited thereto.

[Example]

Polyester film production

Example 1-1

(1) Preparation of co-polyester resin

Based on 100 mol% of terephthalic acid (TPA) as a dicarboxylic acid, 75.6 mol% of ethylene glycol (EG), 18.8 mol% of neopentyl glycol (NPG) and 5.6 mol% of diethylene glycol (DEG) as a diol were mixed with a stirrer and a distillation column Into the attached autoclave (first reactor), manganese acetate as a catalyst for the transesterification reaction was added in an amount of 0.07 parts by weight based on 100 parts by weight of dicarboxylic acid, and then, while the temperature was raised to 220°C, methanol as a by-product was removed and the reaction was carried out. proceeded.

When the transesterification reaction was completed, 0.07 parts by weight of silica having an average particle diameter of 0.28 μm relative to 100 parts by weight of dicarboxylic acid was added, and 0.4 parts by weight of trimethyl phosphate as a stabilizer was added. After 5 minutes, 0.035 parts by weight of antimony trioxide and 0.005 parts by weight of tetrabutyl titanate were added as polymerization catalysts, and the mixture was stirred for 10 minutes. Thereafter, the reactant was transferred to the second reactor equipped with a vacuum facility, and the pressure was gradually reduced while raising the temperature to 285°C, and polymerization was performed for 210 minutes to obtain a copolymerized polyester resin.

(2) Preparation of film

To 90 parts by weight of the co-polyester resin prepared in step (1), 10 parts by weight of a homo polyethylene terephthalate (HOMO-PET) resin (CTF41, manufacturer: SKC Co., Ltd.) (the co-polyester resin and the homo polyethylene terephthalate) 10% by weight based on a total of 100 weight of phthalate (HOMO-PET) resin) was added, and the resultant was extruded at 280° C. with a T-die and cooled to obtain an unstretched sheet.

Then, the unstretched sheet was passed through a roll while feeding at a speed of 55 m/min to control the thickness. The unstretched sheet was preheated at 105° C. for 0.1 minutes while being transferred at a speed of 55 m/min, and stretched 4.15 times in the transverse direction (TD) at 83° C. Thereafter, the stretched sheet was heat-set at a temperature of 75° C. for 0.1 minutes to prepare a polyester film having a thickness of 40 μm.

Examples 1-2 to 1-10 and Comparative Examples 1-1 to 1-9

A polyester film was prepared in the same manner as in Example 1-1, except that the content of carboxylic acid and diol was changed, and the addition amount of homo polyethylene terephthalate and process conditions were changed as shown in Table 1 below. .

The final components of the polyester films prepared in Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-9 are shown in Table 2 below.

division HOMO-PET
(parts by weight) draw ratio Preheat temperature (℃) Heat setting temperature (℃) TD MD Example 1-1 10 4.15 - 105 75 Example 1-2 3 4.15 - 105 85 Examples 1-3 5 4.15 - 105 90 Examples 1-4 - 4.05 - 105 75 Examples 1-5 5 4.15 - 105 75 Examples 1-6 10 4.15 - 105 75 Examples 1-7 20 4.15 - 105 75 Examples 1-8 20 4.5 - 115 70 Examples 1-9 10 4.15 - 105 93 Examples 1-10 30 4.15 - 105 75 Comparative Example 1-1 - 4.5 - 115 70 Comparative Example 1-2 - 4.5 - 115 75 Comparative Example 1-3 - 4.5 - 115 85 Comparative Example 1-4 - 4.5 - 115 90 Comparative Example 1-5 40 4.15 - 105 77 Comparative Example 1-6 60 4.15 - 105 70 Comparative Example 1-7 80 4.15 - 105 75 Comparative Examples 1-8 - 4.5 - 115 75 Comparative Example 1-9 - 4.5 - 115 75

TPA
(mole%) EG
(mole%) NPG
(mole%) CHDM
(mole%) DEG
(mole%) Example 1-1 100 78.0 17.0 - 5.0 Example 1-2 100 78.0 17.0 - 5.0 Examples 1-3 100 78.2 16.9 - 4.9 Examples 1-4 100 78.0 17.0 - 5.0 Examples 1-5 100 79.9 15.9 - 4.2 Examples 1-6 100 80.4 15.4 - 4.2 Examples 1-7 100 82.1 13.9 - 4.0 Examples 1-8 100 72.0 24.0 - 4.0 Examples 1-9 100 80.0 16.0 - 4.0 Examples 1-10 100 80.0 16.0 - 4.0 Comparative Example 1-1 100 71.0 24.0 - 5.0 Comparative Example 1-2 100 71.0 24.0 - 5.0 Comparative Example 1-3 100 71.0 24.0 - 5.0 Comparative Example 1-4 100 71.0 24.0 - 5.0 Comparative Example 1-5 100 86.3 10.0 - 3.7 Comparative Example 1-6 100 90.6 6.3 - 3.1 Comparative Example 1-7 100 94.5 3.4 - 2.1 Comparative Examples 1-8 100 66.4 - 23.0 10.6 Comparative Example 1-9 100 66.6 - 23.1 10.3

* NPG: neopentyl glycol

* CHDM: 1,4-cyclohexanedimethanol

* DEG: Diethylene glycol

Experimental Example 1-1: Melting Point (Tm)

4 mg of the polyester film samples of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-9 prepared above were put into a differential scanning calorimeter (Q2000, manufacturer: TA Instruments), and a differential scanning calorimeter (DSC) mode was used to scan at a heating rate of 10 °C/min.

In the heat flow curve obtained by scanning, the first endothermic temperature is the glass transition temperature (Tg), the exothermic temperature measured after the glass transition temperature (Tg) is the crystallization temperature (Tc), and the crystallization temperature (Tc) is measured after The endothermic temperature was measured as the melting point (Tm). At this time, the integral value at the melting point (Tm) was calculated as the melting enthalpy. Specifically, the melting enthalpy is the energy in the section where endotherm occurs in the heat flow curve of the differential scanning calorimeter, and the trend line from the melting start temperature to the complete melting temperature is set as the baseline, and the integral value of the peak along the baseline is converted was calculated.

5 shows a differential scanning calorimetry (DSC) curve of the polyester film of Examples 1-3.

Experimental Example 1-2: Peel force

Figure 3 shows a method of measuring the peel force of the polyester film. That is, FIG. 3 shows a method of testing the seaming property, which is the adhesive force of the polyester film by the solvent.

Specifically, first, two samples of the polyester films of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-9 (first polyester film and second polyester film) prepared above in A4 Each size was prepared.

Thereafter, 1,3-dioxolane is applied to one surface of the first polyester film 100 in the form of a band having a width of 2 mm and a length of 30 mm to form the adhesive part 110 while the adhesive part is formed on the first polyester film. A second polyester film 200 was laminated on it (FIG. 3(a)). In this case, the adhesive part 110 was formed at a position separated by 6.5 cm (w) from the upper end of the first polyester film 100 . In addition, the area of the bonding part 110 was 60 mm ² .

Thereafter, a pressure plate 120 was placed on the second polyester film in order to prevent the laminated first polyester film and the second polyester film from being bent. Thereafter, a weight 130 of 2 kg was placed on the pressure plate 120 and aged for 1 hour (FIG. 3(b)). At this time, the weight 130 is placed at the position of the adhesive portion (110).

Thereafter, the weight 130 and the pressing plate 120 were removed, and the laminated first polyester film and the second polyester film were cut to 3 cm in width and 9 cm in length to obtain a sample 300 ( Fig. 3(c)).

Thereafter, the maximum force measured by peeling the first polyester film 100 and the second polyester film 200 from the sample 300 at a speed of 300 mm/min and an angle of 180° was measured as the peeling force. (Fig. 3(d)).

The above experiment was performed 5 times, and the average value is shown in Table 3 below.

Experimental Example 1-3: heat shrinkage

Figure 4 shows a method for measuring the thermal shrinkage of the polyester film. Referring to Figure 4, the polyester film 100 of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-9 prepared above 300 mm in the direction to be measured and in a direction perpendicular thereto, respectively. It was cut to 15 mm. In this case, the 300 mm is the first dimension (x1) before shrinkage, and the 15 mm is the second dimension (y) ( FIG. 4( a )).

The cut polyester film 100 is immersed in a heated water bath for 10 seconds to measure the contracted dimension of the polyester film 100a after shrinkage, that is, the first dimension (x2) after shrinkage (FIG. 4 ( b)), and was calculated according to Equation 2 below. The thermal contraction rate (%) in this experimental example was obtained for the main shrinkage direction (TD) and the direction perpendicular thereto (MD), respectively.

[Equation 2]

division Tm (℃) Peel force (gf/3 cm) Example 1-1 201.1 600 Example 1-2 202.8 400 Examples 1-3 208.2 345 Examples 1-4 200.8 750 Examples 1-5 208.2 659 Examples 1-6 211.8 489 Examples 1-7 220.0 361 Examples 1-8 199.5 1010 Examples 1-9 223.9 412 Examples 1-10 229.0 350 Comparative Example 1-1 185.1 2208 Comparative Example 1-2 188.7 2012 Comparative Example 1-3 188.9 1357 Comparative Example 1-4 184.6 870 Comparative Example 1-5 233.7 120 Comparative Example 1-6 240.7 80 Comparative Example 1-7 247.1 50 Comparative Examples 1-8 161.4 2514 Comparative Example 1-9 160.4 2317

division TD heat shrinkage (%) MD heat shrinkage (%) 70℃ 80℃ 90℃ 100℃ 70℃ 75℃ 80℃ 90℃ 100℃ Example 1-1 25.0 58.0 70.0 73.0 -1.0 -0.5 0.0 1.8 2.8 Example 1-2 10.0 46.0 60.0 66.0 0.0 -2.2 -0.6 0.9 2.4 Examples 1-3 4.0 25.0 42.0 51.0 0.0 -1.1 -1.7 1.2 2.3 Examples 1-4 25.7 68.3 76.3 77.0 0.0 -3.3 -1.7 2.8 3.9 Examples 1-5 26.7 67.3 75.3 76.3 2.2 -2.2 -1.7 2.8 3.3 Examples 1-6 23.7 67.0 72.3 74.0 2.2 -2.2 -2.8 0.0 0.6 Examples 1-7 26.0 63.3 73.7 75.0 3.3 0.6 0.0 4.4 5.6 Examples 1-8 45.0 75.0 78.0 78.0 -1.2 -4.2 -2.1 3.4 5.8 Examples 1-9 0.6 57.2 72.2 76.1 -0.8 1.2 0.0 2.8 4.8 Examples 1-10 25.0 51.0 68.3 72.0 0 -2.3 -1.3 0.7 2.3 Comparative Example 1-1 51.0 78.0 79.7 80.0 -6.7 -5.0 0.0 2.3 2.7 Comparative Example 1-2 33.0 73.0 79.3 80.0 -5.3 -8.6 -4.0 1.0 1.7 Comparative Example 1-3 5.3 52.7 74.3 78.7 -0.7 -3.3 -4.0 -2.0 1.7 Comparative Example 1-4 2.7 26.7 56.3 67.3 -0.7 -1.7 -4.0 -6.0 -4.7 Comparative Example 1-5 14.0 53.0 66.3 68.3 5.6 8.3 5.0 3.9 7.2 Comparative Example 1-6 9.3 37.0 53.7 55.0 5.8 7.2 6.3 4.4 7.6 Comparative Example 1-7 5.0 19.0 37.3 41.0 6.2 8.5 7.2 6.1 8.0 Comparative Examples 1-8 37.0 73.3 79.7 79.7 -5.8 -4.7 -1.7 0.7 2.7 Comparative Example 1-9 28.3 63.3 69.3 78.3 -1.0 -4.3 -3.7 -2.0 1.0

As shown in Tables 3 and 4, the polyester films of Examples 1-1 to 1-10 had melt enthalpy, peel force, and thermal contraction rate for each temperature all within the preferred range.

Specifically, since the polyester film of Examples 1-1 to 1-10 satisfies the preferred range of adhesive strength after the seaming process, it can be seen that it is suitable for application as a heat-shrinkable film. In addition, the polyester film of Examples 1-1 to 1-10 has a very low clumping fraction during the regeneration process of the film or a polyethylene terephthalate (PET) container including the film or the film by adjusting the melting enthalpy within the above range. Recyclability can be improved while preventing environmental pollution.

Manufacture of recycled polyester chips

Example 2-1

(1) Preparation of a polyethylene terephthalate container equipped with a polyester film

1 shows before and after heat shrinkage of a polyester film applied to a product. Referring to Figure 1, a portion of the outer surface of the polyethylene terephthalate container (PET container, 30 g) was wrapped with the polyester film of Example 1-1 prepared above (Figure 1 (a)). At this time, it was fixed using an acrylic adhesive. Thereafter, the polyester film of Example 1-1 was shrunk at a temperature of 90° C. and hot air conditions to obtain a polyethylene terephthalate container equipped with a polyester film (FIG. 1(b)).

(2) Regeneration process of polyethylene terephthalate container

The container provided with the polyester film prepared in step (1) was pulverized with a grinder to obtain flakes. The flakes were first washed with water. Thereafter, a second washing was performed for 15 minutes with a washing solution (a mixture of 0.3 parts by weight of Triton X-100 solution and 1.0 parts by weight of NaOH solution) stirred in a water bath at 88°C at 880 rpm. Thereafter, the second washed flakes were washed three times with water at room temperature to remove the residual washing solution, and dried at 160° C. for 20 minutes. Thereafter, a regenerated polyester chip was prepared by heat treatment at 210° C. for 90 minutes.

Examples 2-2 to 2-9 and Comparative Examples 2-1 to 2-9

In the same manner as in Example 2-1, except that the polyester films of Examples 1-2 to 1-9 and Comparative Examples 1-1 to 1-9 were used instead of the polyester film of Example 1-1. Recycled polyester chips were prepared.

Experimental Example 2-1: Clumping ratio

According to the polyethylene terephthalate flake clump evaluation (APR PET-S-08) procedure of the American Association of Plastic Recyclers (APR), the clumping fraction (%) was measured.

2 shows a method for measuring the clumping of a polyethylene terephthalate (PET) container equipped with a polyester film.

Specifically, the product 1 provided with the label 11a with the polyester film in the polyethylene terephthalate (PET) container 20 is pulverized in the grinder 6, and the first sieve (0.374" sieve with a hole size of 9.5 mm) . As the product (1), the polyester containers of Examples 2-1 to 2-10 and Comparative Examples 2-1 to 2-9 prepared above were used (FIGS. 1 and 2(a)).

Then, the mixed flakes were put into a cylinder having a diameter of 6 cm and a height of 8 cm, and a weight 7 of 2.5 kg was placed thereon and a pressure of 8.7 kPa was applied thereto. Thereafter, the additionally raised cylinder was heat-treated in a convection oven at 210° C. for 90 minutes and then cooled at room temperature ( FIG. 2( b )).

Thereafter, the cooled mixed flakes are sieved using a second sieve (8, 0.625" sieve) having a hole diameter d of 11.2 mm, and the agglomerated mixed flakes 10b remaining on the second sieve 8. (Fig. 2(c)) The weight of the mixed flakes was measured and calculated according to Equation 1 below.

[Equation 1]

division Clumping fraction (%) Example 2-1 3.8 Example 2-2 6.2 Example 2-3 5.5 Example 2-4 7.2 Example 2-5 0.0 Example 2-6 0.0 Example 2-7 0.0 Examples 2-8 0.0 Examples 2-9 0.0 Example 2-10 0.0 Comparative Example 2-1 11.7 Comparative Example 2-2 16.1 Comparative Example 2-3 22.7 Comparative Example 2-4 14.5 Comparative Example 2-5 0.0 Comparative Example 2-6 0.0 Comparative Example 2-7 0.0 Comparative Example 2-8 21.3 Comparative Example 2-9 18.6

As shown in Table 5, the recycled polyester chips of Examples 2-1 to 2-10 have a very low clumping fraction, so they are advantageous for a long-time high-temperature process during the regeneration process, thereby improving recyclability.

Specifically, as shown in Table 2, by using a polyester film that satisfies a specific melting enthalpy and has excellent mechanical properties, the recycled polyester chips of Examples 2-1 to 2-10 had a very low clumping fraction.

On the other hand, the recycled polyester chips of Comparative Examples 2-1 to 2-4, 2-8, and 2-9 had very high clumping fractions and thus had low reproducibility. On the other hand, the recycled polyester chips of Comparative Examples 2-5 to 2-7 have a low clumping fraction, but as shown in Table 2 above, the thermal properties and seaming properties of the polyester film are not good, so it is difficult to apply to various products. .

d: diameter of hole
x1: first dimension before shrinkage
x2: first dimension after shrinkage
y: second dimension
w: the length to the bonding part
TL; Trendline
T1: melting start temperature
T2: full melting temperature
1: Labeled products
6: Grinder
7: Chu
8: sieve
10a: second flake
10b: agglomerated mixed flakes
11: (pre-shrink) label
11a: label after shrinkage
20: product
20a: first flake
100: (first before shrinkage) polyester film
100a: polyester film after shrinkage
110: adhesive part
120: press plate
130: weight
200: second polyester film
300: Sample A

Claims (8)

co-polyester resin in which diol and dicarboxylic acid are copolymerized; and
Contains a homo polyethylene terephthalate (HOMO-PET) resin,
The diol comprises ethylene glycol, neopentyl glycol and 1 mol% to 8 mol% of diethylene glycol,
The dicarboxylic acid comprises terephthalic acid,
0.5 wt% to 25 wt% of the homo polyethylene terephthalate (HOMO-PET) resin based on a total of 100 weight of the copolymerized polyester resin and the homo polyethylene terephthalate (HOMO-PET) resin,
The melting point (Tm) measured by Differential Scanning Calorimetry is 190°C to 230°C,
a clumping ratio of 10% or less,
A polyester film having a peel force of 150 gf/3 cm or more. delete The method of claim 1,
A polyester film having a thermal contraction rate of 45% to 85% in the first direction during heat treatment at a temperature of 100°C for 10 seconds. 4. The method of claim 3,
A polyester film having a thermal contraction rate of 7% or less in the second direction perpendicular to the first direction during heat treatment at a temperature of 100° C. for 10 seconds. The method of claim 1,
The polyester film, wherein the diol contains ethylene glycol, and 10 mol% or more of one or more comonomers selected from the group consisting of neopentyl glycol and diethylene glycol. The method of claim 1,
A polyester film comprising neopentyl glycol in an amount of 5 mol% to 35 mol%. preparing a copolymerized polyester resin in which diol and dicarboxylic acid are copolymerized;
After adding a homo polyethylene terephthalate (HOMO-PET) resin to the copolymer polyester resin, melt extrusion at a temperature of 250 ° C. to 300 ° C. to prepare an unstretched sheet; and
After stretching the unstretched sheet, heat-setting at a temperature of 70° C. to 100° C. to prepare a polyester film,
The diol comprises ethylene glycol, neopentyl glycol and 1 mol% to 8 mol% of diethylene glycol,
The dicarboxylic acid comprises terephthalic acid,
0.5 wt% to 25 wt% of the homo polyethylene terephthalate (HOMO-PET) resin is added based on a total of 100 weight of the copolymerized polyester resin and the homo polyethylene terephthalate (HOMO-PET) resin,
A melting point (Tm) of the polyester film measured by Differential Scanning Calorimetry is 190°C to 230°C,
A clumping ratio of the polyester film is 10% or less, and a peeling force of 150 gf/3 cm or more, a method for producing a polyester film. Preparing a polyethylene terephthalate (PET) container equipped with the polyester film according to claim 1;
pulverizing a polyethylene terephthalate (PET) container equipped with the film to obtain flakes; and
heat-treating the flakes to produce recycled polyester chips,
A clumping ratio of the flakes is 10% or less,
The method for recycling a polyethylene terephthalate container, wherein the flakes include a first flake obtained by pulverizing the polyethylene terephthalate (PET) container and a second flake obtained by pulverizing the polyester film.

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