Oriented polyester film and method for producing the same

Abstract

The present invention relates to an oriented polyester film and a method for producing the same. The oriented polyester film comprises a polyester resin in which a diol component and a dicarboxylic acid component are polymerized, and when analyzed by differential scanning calorimetry (DSC) after a first heat treatment and a second heat treatment, the oriented polyester film exhibits a first melting point (Tm1) and a second melting point (Tm2), and the ratio (H2 / H1) of the second heat of fusion (H2) at the second melting point (Tm2) to the first heat of fusion (H1) at the first melting point (Tm1) is 0.1 or higher. The oriented polyester film according to the present invention can be usefully used as a heat-shrinkable film applied as a label and / or packaging for plastic containers, and in particular, because it has extremely excellent crystallinity, it improves the efficiency of the recycling process for waste plastic containers.

Description

Detailed description of the invention

[0001] [Technical field] The present invention relates to an oriented polyester film having excellent crystallinity for improving heat shrinkability and the efficiency of the regeneration process, and to a method for preparing this oriented polyester film.

[0002] [Background technology] Polyester is used as a material in various fields due to its excellent mechanical strength, heat resistance, transparency, and gas barrier properties among polymers. In particular, heat-shrinkable films prepared using polyester resin are suitable for packaging and / or labels for plastic containers such as PET bottles, due to their high heat resistance and appropriate heat shrinkage rate.

[0003] On the other hand, while the use of plastic containers makes daily life more convenient, their indiscriminate disposal or excessive use has led to extremely serious environmental problems. Therefore, various methods for recycling used plastic containers are being developed.

[0004] The process of recycling waste plastic containers can be divided into a physical recycling process involving washing and crushing, and a chemical recycling process involving depolymerization. However, these recycling processes require pretreatment to separate the waste plastics by type, and this process reduces the efficiency of the recycling process. For example, recycling a PET bottle with a polyester film label requires separating (removing) the polyester film from the PET bottle. This is because there is a difference in crystallinity between the polyester resin contained in the polyester film and the PET contained in the PET bottle, and therefore, if a PET bottle with a polyester film attached is subjected to the recycling process, the recycling process will not function.

[0005] Therefore, in order to improve the efficiency of the recycling process, it is necessary to develop a technology that can eliminate the pre-treatment step of separating (removing) the polyester film from plastic containers such as PET bottles.

[0006] [Prior art document] [Patent Document 1] Korean Published Patent No. 2009-0062882

[0007] [Disclosure of the Invention] [Technical issues] To solve the aforementioned problems in the prior art, the inventors conducted various studies. As a result, they discovered that an oriented polyester film that can be subjected to a recycling process without being separated (removed) from waste plastic containers can be obtained by maximizing the crystallinity of an oriented polyester film prepared using polyester resin.

[0008] Therefore, the object of the present invention is to provide an oriented polyester film having excellent crystallinity and a method for preparing the same.

[0009] [Solutions to the problem] To solve the aforementioned problems, the present invention provides an oriented polyester film comprising a polyester resin in which a diol component and a dicarboxylic acid component are polymerized, wherein when the film is subjected to a first heat treatment and a second heat treatment and subsequently analyzed by differential scanning calorimetry (DSC), a first melting point (Tm1) and a second melting point (Tm2) appear, and the ratio (H2 / H1) of the second heat of fusion (H2) at the second melting point (Tm2) to the first heat of fusion (H1) at the first melting point (Tm1) is 0.1 or greater.

[0010] Furthermore, the present invention provides an oriented polyester film containing a polyester resin in which a diol component and a dicarboxylic acid component are polymerized, wherein an oriented polyester film sample obtained by subjecting the oriented polyester film to a first heat treatment at 70°C, a preliminary heat treatment at 160°C, and then cutting it into 1 cm × 1 cm pieces is mixed with a polyethylene terephthalate (PET) sample obtained by passing a PET container through a 12.5 mm mesh sieve in a weight ratio of 3:97. This mixed sample is heat-treated at 195°C for 90 minutes, and when the heat-treated mixed sample is passed through the sieve to evaluate the crystallinity of the polyester oriented film, the crystal fraction represented by the following formula 2 is 30% or more.

[0011] [Formula 2] Crystal fraction (%) = (F T / F m ) × 100

[0012] In formula 2, F T is the ratio ((S s ) / M T ) × 100, %) of the weight (S s ) of the sample that passed through the 12.5 mm mesh sieve among the heat-treated mixed sample to the total weight (M T ) of the heat-treated mixed sample, and F m is the ratio ((C s ) / M T ) × 100, %) of the weight (C s ) of the aggregated sample remaining on the 12.5 mm mesh sieve among the heat-treated mixed sample to the total weight (M T ) of the heat-treated mixed sample.

[0013] <照 Furthermore, the present invention provides a method for preparing an oriented polyester film, comprising polymerizing a diol component and a dicarboxylic acid component to prepare a polyester resin, preparing an oriented polyester sheet from the polyester resin, and heat-fixing the oriented sheet, wherein when the film is subjected to a first heat treatment and a second heat treatment and subsequently analyzed by differential scanning calorimetry (DSC), a first melting point (Tm1) and a second melting point (Tm2) appear, and the ratio (H2 / H1) of the second heat of fusion (H2) at the second melting point (Tm2) to the first heat of fusion (H1) at the first melting point (Tm1) is 0.1 or greater.

[0014] [Advantageous effects of the invention] The oriented polyester film according to the present invention has multiple melting points (T m It possesses the following properties, and when heat-treated two or more times under specific conditions, it satisfies a specific range of heat of fusion ratios, and consequently exhibits excellent thermal shrinkage along with maximized crystallinity.

[0015] Therefore, the oriented polyester film according to the present invention can be advantageously used as a heat-shrinkable film for labels on packaging and / or plastic containers (e.g., PET bottles).

[0016] Furthermore, the oriented polyester film according to the present invention has high crystallinity. In the recycling process of used plastic containers, it may be possible to recycle the plastic containers without separating the oriented polyester film (for example, it is possible to recycle plastic containers with the oriented polyester film still attached). As a result, the present invention can improve the efficiency of the recycling process compared to the prior art. [Brief explanation of the drawing]

[0017] [Figure 1] This graph shows the DSC analysis results of the oriented polyester film prepared in Example 6 of the present invention.

[0018] [Best mode for carrying out the invention] The present invention will now be described in detail. The present invention as described herein is not limited to the disclosures shown below and can be modified in various forms as long as the essence of the invention is not altered.

[0019] In this specification, the term "~including" is intended to specify a particular feature, area, step, process, element, and / or component. Unless otherwise explicitly stated, the term "~including" does not exclude the presence or addition of other features, areas, steps, processes, elements, and / or components.

[0020] Throughout this specification, terms such as "first," "second," etc., are used to describe various components. However, these terms should not limit the components. These terms are used for the purpose of distinguishing one element from another.

[0021] In this specification, all numerical and quantitative expressions relating to components, reaction conditions, etc., should be understood to be modified by the term “approximately” unless otherwise indicated.

[0022] Generally, the melting point (T) of polymer resins m ) is the crystallization temperature (T c It is defined as the limiting point of the polymer resin, and is the temperature at which the crystalline portion begins to melt. Multiple melting points (T m A polymer resin having ) requires a large amount of heat to melt the crystalline portion, which can be interpreted as meaning that the crystallinity of the polymer resin is maximized.

[0023] Based on the above, the oriented polyester film of the present invention, which contains a polyester resin, a polymer resin, undergoes a first heat treatment and a second heat treatment under specific conditions to reach multiple melting points (T m It possesses the following properties. The ratio of heats of fusion at these multiple melting points satisfies a specific range, and it exhibits high crystallinity.

[0024] In particular, in an oriented polyester film according to one embodiment, the oriented polyester film can be shrunk through a first heat treatment, and the crystallinity of the oriented polyester film can be strengthened through a second heat treatment.

[0025] In addition, the crystallinity of the oriented polyester film can be optimized by controlling various second heat treatment conditions. This optimized crystallinity makes the oriented polyester film advantageously usable as a heat-shrinkable film for labels on packaging and / or plastic containers (e.g., PET bottles). Furthermore, in the recycling process of used plastic containers, it is technically significant that the recycling process can be carried out without separating the oriented polyester film (polyester film) (for example, plastic containers with the oriented polyester film still attached can be recycled), thus significantly improving the efficiency of the recycling process.

[0026] This will be explained in detail below. (Stretched polyester film) An oriented polyester film according to one embodiment contains a polyester resin in which a diol component and a dicarboxylic acid component are polymerized, and when the film is subjected to a first heat treatment and a second heat treatment and then analyzed by differential scanning calorimetry (DSC), a first melting point (Tm1) and a second melting point (Tm2) appear, and the ratio (H2 / H1) of the second heat of fusion (H2) at the second melting point (Tm2) to the first heat of fusion (H1) at the first melting point (Tm1) is 0.1 or greater.

[0027] Specifically, this oriented polyester film is an oriented film containing polyester resin. Excellent thermal shrinkage can be achieved by heat treatment at a first heat treatment temperature. When the oriented polyester film shrunk by heating at the first heat treatment temperature is subjected to heat treatment at a second heat treatment temperature, the crystallinity of the heated oriented polyester film is optimally enhanced, thereby making it possible to obtain a heat-shrinkable film with enhanced crystallinity while maintaining excellent thermal shrinkability.

[0028] The crystallinity of oriented polyester films can serve as an indicator of their recyclability and the efficiency of the regeneration process. In other words, as the crystallinity of oriented polyester films increases, their recyclability increases and the efficiency of the regeneration process can be enhanced.

[0029] The crystallinity of the oriented polyester film according to one embodiment can be optimally enhanced through two or more heat treatment processes. As a result, when the oriented polyester film is attached to a waste plastic container, the melting of the film together with the waste plastic container during the recycling process is reduced. Therefore, the recycling process of the waste plastic container may be carried out without the step of separating (removing) the oriented polyester film from the waste plastic container, thereby improving the efficiency of the recycling process.

[0030] Furthermore, the oriented polyester film according to the present invention may be a polyester film prepared by heat-treating an oriented film prepared from a polyester resin two or more times.

[0031] Specifically, the oriented polyester film according to the present invention may be a polyester film prepared by heat-treating an oriented film prepared from a polyester resin at a first heat treatment temperature, and then heat-treating it again at a second heat treatment temperature. Furthermore, the oriented polyester film according to the present invention may be a polyester film prepared by one or more heat treatments performed at a second heat treatment temperature.

[0032] For example, the oriented polyester film may be a polyester film prepared by two or more heat treatments, particularly two or three. Specifically, the oriented polyester film may be a polyester film prepared by, for example, a first heat treatment and a second heat treatment, or by a first heat treatment, a preheating treatment for the second heat treatment, and the second heat treatment.

[0033] In this specification, the oriented polyester film may include a film obtained by melting a polyester resin to form a sheet, and then stretching this sheet.

[0034] Specifically, the oriented polyester film may be an oriented film prepared through a melt casting step, a stretching step, and / or a heat setting step of a polyester resin. Specific processing methods for the polyester oriented film are described below.

[0035] According to one embodiment, the first heat treatment temperature may be 60 to 105°C, specifically 62 to 104°C, 62 to 103°C, 65 to 102°C, 68 to 100°C, 70 to 100°C, 70 to 98°C, 70 to 97°C, or 70 to 96°C.

[0036] The first heat treatment is a shrinkage process for the oriented polyester film. When the first heat treatment temperature meets the aforementioned range, the oriented polyester film can achieve a desired level of excellent heat shrinkage.

[0037] In addition, the second heat treatment temperature may be 140-220°C, specifically 141-219°C, 142-218°C, 143-217°C, 144-216°C, 145-215°C, 145-214°C, 146-213°C, or 150-210°C.

[0038] The second heat treatment is a crystallization process for the polyester film that has been shrunk by the first heat treatment. When the second heat treatment temperature meets the aforementioned range, the oriented polyester film can achieve a desired level of excellent crystallinity.

[0039] In other words, when the first and second heat treatments are performed on the oriented polyester film, excellent thermal shrinkage and high crystallinity can be achieved simultaneously.

[0040] In particular, when the first and second heat treatment temperatures each satisfy the aforementioned ranges, the oriented polyester film according to the present invention can obtain high crystallinity and excellent heat shrinkage to the required level.

[0041] Furthermore, the second heat treatment condition can also be changed to adjust the crystallinity.

[0042] For example, the second heat treatment may be carried out by a preheating treatment of the oriented polyester film that has been subjected to the first heat treatment (preheating treatment for the second heat treatment), followed by the second heat treatment.

[0043] Specifically, the second heat treatment may include a preheating treatment of the orientation polyester film after it has been subjected to the first heat treatment, and a second heat treatment of the orientation polyester film after it has been subjected to the preheating treatment.

[0044] The preheating treatment may be carried out in the same or similar temperature range as the second heat treatment. For example, the preheating treatment may be carried out at a temperature of 140-220°C, specifically 141-219°C, 142-218°C, 143-217°C, 144-216°C, 145-215°C, 145-214°C, 146-213°C, or 150-210°C for 1-30 minutes, 1-20 minutes, 5-30 minutes, 5-25 minutes, 5-20 minutes, 5-15 minutes, 6-25 minutes, 6-20 minutes, 6-15 minutes, or 6-13 minutes.

[0045] When the preheating treatment is performed within the aforementioned range during the second heat treatment, the oriented polyester film, which has shrunk by the first heat treatment, crystallizes after the preheating treatment. The crystallinity of the oriented polyester film can be maximized to an optimal range after the second heat treatment, thereby further enhancing the efficiency of the regeneration process.

[0046] Furthermore, the differential scanning calorimeter (DSC) used to analyze the oriented polyester film after the first and second heat treatments may specifically be a modulated differential scanning calorimeter (modulated DSC or MDSC), and more specifically, a temperature-modulated differential scanning calorimeter (TMDSC). For analysis by differential scanning calorimetry (DSC), a heating rate condition of 10°C / min to reach 280°C from room temperature can be used.

[0047] According to one embodiment, the first melting point (T) that appears during the first and second heat treatments m1 ) and the second melting point (T m2 The first melting point (T) is not particularly limited, but can be between 150 and 230°C. m1 ) and the second melting point (T m2 These may be different from each other. Specifically, the first melting point (T m1 ) is the second melting point (T m2 It can be lower than ).

[0048] That is, the first melting point (T) after the first heat treatment. m1The temperature range may be 150-230°C, specifically 152-230°C, 154-220°C, 156-220°C, 158-215°C, 160-215°C, 162-215°C, or 162-210°C.

[0049] Furthermore, after the first heat treatment, one or more first melting points (T m1 ) may appear.

[0050] That is, after the first heat treatment, one or more first melting points (T m1 ) may appear, and multiple first melting points (T m1 ) may exhibit different melting points within the aforementioned range.

[0051] In addition, the second melting point (T m2 The temperature range may be 150-230°C, specifically 155-230°C, 170-230°C, 175-229°C, 180-229°C, 185-228°C, 190-228°C, or 195-228°C.

[0052] Specifically, after the second heat treatment, the second melting point (T m2 The melting point (T) is 150°C to 230°C, and the oriented polyester film can be crystalline. In addition, after the second heat treatment, the oriented polyester film has a desired melting point (T) m2 ) and can have an enthalpy at that temperature.

[0053] Here, the first melting point (T m1 ) and the second melting point (T m2 These may be different from each other.

[0054] Furthermore, after the second heat treatment, one or more second melting points (T m2 ) may appear.

[0055] That is, after the second heat treatment, one or more second melting points (T m2 ) may appear, and multiple second melting points (T m2 ) may exhibit different melting points within the aforementioned range.

[0056] First and second melting points (T m1 and T m2 When each of these is within the aforementioned range, the oriented polyester film according to the present invention can have high crystallinity to the required level, along with enhanced heat shrinkage, heat resistance, and durability.

[0057] Furthermore, when the oriented polyester film after the first heat treatment and after the preheating treatment prior to the second heat treatment is analyzed by differential scanning calorimetry (DSC), the second-p melting point (T m2-p ) appears. 2-p melting point (T m2-p The temperature range may be 150-230°C, specifically 155-230°C, 156-230°C, 157-229°C, 160-229°C, 160-228°C, or 160-225°C.

[0058] Furthermore, when the oriented polyester film after the first heat treatment and after the preheating treatment prior to the second heat treatment is analyzed by differential scanning calorimetry (DSC), one or more 2-p melting points (T m2-p ) may appear.

[0059] That is, after the preheating treatment of the orientation polyester film subjected to the first heat treatment, one or more second-p melting points (T m2-p ) may appear, and multiple second-p melting points (T m2-p ) may exhibit different melting points within the aforementioned range.

[0060] 2nd-p melting point (T m2-p When the range is within the aforementioned range, the oriented polyester film can have maximized crystallinity, along with further enhanced heat shrinkage, heat resistance, and durability.

[0061] Furthermore, according to one embodiment, the oriented polyester film has a first melting point (T m1 ) and the second melting point (T m2Each of these materials may have a specific range of heat of fusion (ΔH). Heat of fusion refers to the amount of heat required to melt a substance. By adjusting the heat of fusion and its ratio, the crystallinity can be adjusted to a desired range.

[0062] Specifically, the first melting point (T) after the first heat treatment. m1 The heat of fusion (H1) at ) may be 1.0 J / g or more, 1.5 J / g or more, or 2.0 J / g or more, and 40.0 J / g or less, 35.0 J / g or less, 30.0 J / g or less, 28.0 J / g or less, or 27.0 J / g or less. More specifically, the first melting point (T) after the first heat treatment m1 The heat of fusion (H1) in ) may be, for example, 1.0 J / g to 40.0 J / g, 1.0 J / g to 30.0 J / g, 1.0 J / g to 28.0 J / g, 2.0 J / g to 40.0 J / g, 2.0 J / g to 30.0 J / g, 2.0 J / g to 28.0 J / g, 3.0 J / g to 40.0 J / g, 3.0 J / g to 30.0 J / g, 3.0 J / g to 28.0 J / g, 4.0 J / g to 40.0 J / g, 4.0 J / g to 30.0 J / g, 4.0 J / g to 28.0 J / g, 4.8 J / g to 40.0 J / g, 4.8 J / g to 30.0 J / g, or 4.8 J / g to 28.0 J / g.

[0063] First melting point (T) after the first heat treatment m1 If the heat of fusion (H1) in ) satisfies the aforementioned range, then the heat of fusion (H1) may be advantageous for the purpose of satisfying the desired thermal shrinkage rate and crystallinity. In particular, the oriented polyester film according to the present invention is prepared from an oriented film containing a polyester resin. In such a case, the oriented film exhibits excellent thermal shrinkage after a first heat treatment, and the oriented polyester film prepared from such an oriented film has excellent thermal shrinkage.

[0064] Also, one or more first melting points (T m1 ) appears after the first heat treatment, and the total heat of fusion (H 1T) may be 1.0 J / g or more, 1.5 J / g or more, or 2.0 J / g or more, and 40.0 J / g or less, 35.0 J / g or less, 30.0 J / g or less, 25.0 J / g or less, or 20.0 J / g or less. More specifically, the total heat of fusion (H) after the first heat treatment. 1T For example, the values ​​may be 1.0 J / g to 40.0 J / g, 1.0 J / g to 30.0 J / g, 1.0 J / g to 28.0 J / g, 2.0 J / g to 40.0 J / g, 2.0 J / g to 30.0 J / g, 2.0 J / g to 28.0 J / g, 3.0 J / g to 40.0 J / g, 3.0 J / g to 30.0 J / g, 3.0 J / g to 28.0 J / g, 4.0 J / g to 40.0 J / g, 4.0 J / g to 30.0 J / g, 4.0 J / g to 28.0 J / g, 4.8 J / g to 40.0 J / g, 4.8 J / g to 30.0 J / g, or 4.8 J / g to 28.0 J / g.

[0065] Total heat of fusion (H 1T If the above range is met, the total heat of fusion (H 1T ) may be more advantageous for the purpose of achieving the desired effect.

[0066] In addition, the second melting point (T) after the second heat treatment m2 The second heat of fusion (H2) at ) may be greater than 0.0 J / g, 0.1 J / g or more, 0.5 J / g or more, 1.0 J / g or more, or 1.5 J / g or more, and less than 50.0 J / g, 45.0 J / g or less, 40.0 J / g or less, 35.0 J / g or less, or 30.0 J / g or less. More specifically, the second melting point (T) after the second heat treatment m2The second heat of fusion (H2) in ) is, for example, greater than 0.0 J / g and less than 50.0 J / g, 0.1 J / g to 49.0 J / g, 0.1 J / g to 45.0 J / g, 0.1 J / g to 40.0 J / g, 0.5 J / g to 49.0 J / g, 0.5 J / g to 45.0 J / g, 0.5 J / g to 40.0 J / g, 0.5 J / g to 33.0 J / g, 0.5 J / g to 30.0 J / g, It may also be 1.0 J / g to 49.0 J / g, 1.0 J / g to 45.0 J / g, 1.0 J / g to 40.0 J / g, 1.0 J / g to 33.0 J / g, 1.0 J / g to 30.0 J / g, 1.5 J / g to 49.0 J / g, 1.5 J / g to 45.0 J / g, 1.5 J / g to 40.0 J / g, 1.5 J / g to 33.0 J / g, or 1.5 J / g to 30.0 J / g.

[0067] Second melting point (T) after the second heat treatment m2 If the second heat of fusion (H2) in ) satisfies the aforementioned range, then that second heat of fusion (H2) may be even more advantageous for the purpose of satisfying the desired thermal shrinkage and crystallinity.

[0068] After the second heat treatment, one or more second melting points (T m2 ) appears, and the total heat of fusion (H 2T ) may be 1.0 J / g or more or 1.5 J / g or more, and less than 50.0 J / g, 49.0 J / g or less, 45.0 J / g or less, 40.0 J / g or less, 35.0 J / g or less, or 30.0 J / g or less. More specifically, the total heat of fusion (H 2T For example, the values ​​may be 1.0 J / g to 49.0 J / g, 1.0 J / g to 45.0 J / g, 1.0 J / g to 40.0 J / g, 1.0 J / g to 33.0 J / g, 1.0 J / g to 30.0 J / g, 1.5 J / g to 49.0 J / g, 1.5 J / g to 45.0 J / g, 1.5 J / g to 40.0 J / g, 1.5 J / g to 33.0 J / g, or 1.5 J / g to 30.0 J / g.

[0069] Total heat of fusion (H 2T If the above range is met, the total heat of fusion (H 2T ) may be more advantageous for the purpose of achieving the desired effect.

[0070] Furthermore, the oriented polyester film after the first heat treatment and the preheating treatment prior to the second heat treatment has a second-p melting point (T) of 1.0 J / g or more, 1.5 J / g or more, or 2.0 J / g or more, and 40.0 J / g or less, 35.0 J / g or less, or 33.0 J / g or less. m2-p ) Heat of fusion of 2-p (H 2-p ) may have. More specifically, the second-p melting point (T m2-p ) Heat of fusion of 2-p (H 2-p For example, the values ​​may be 1.0 J / g to 40.0 J / g, 1.0 J / g to 38.0 J / g, 1.0 J / g to 35.0 J / g, 2.0 J / g to 40.0 J / g, 2.0 J / g to 38.0 J / g, 2.0 J / g to 35.0 J / g, 3.0 J / g to 40.0 J / g, 3.0 J / g to 38.0 J / g, 3.0 J / g to 35.0 J / g, 4.0 J / g to 40.0 J / g, 4.0 J / g to 38.0 J / g, 4.0 J / g to 35.0 J / g, 4.7 J / g to 40.0 J / g, 4.7 J / g to 38.0 J / g, or 4.7 J / g to 35.0 J / g.

[0071] The oriented polyester film after the first heat treatment and preheat treatment satisfies the aforementioned range, and has a second-p melting point (T m2-p If the film has a second-p heat of fusion (H2-p) in the ), the crystallinity of the film can be maximized, thereby further enhancing the efficiency of the regeneration process.

[0072] Furthermore, the crystallinity of the oriented polyester film is determined by the second melting point (T m2 The second heat of fusion (H2) at ) is the first melting point (T m1 It can vary depending on the ratio (H2 / H1) of the first heat of fusion (H1) in ).

[0073] Specifically, the second melting point (T m2 The second heat of fusion (H2) at ) is the first melting point (T m1The ratio (H2 / H1) to the first heat of fusion (H1) in ) may be 0.1 or greater, for example, 0.1-10.0, 0.2-9.5, 0.3-9.0, 0.3-8.5, 0.3-8.0, 0.3-7.0, 0.3-6.0, 0.3-5.0, 0.3-4.0, 0.3-3.8, 0.3-3.5, 0.3-3.0, 0.3-2.9, 0.3-2.5, 1.0-3.5, 1.0-3.4, or 1.0-3.0.

[0074] Second melting point (T m2 The second heat of fusion (H2) at ) is the first melting point (T m1 When the ratio (H2 / H1) to the first heat of fusion (H1) in ) satisfies the aforementioned range, it is possible to enhance crystallinity while simultaneously achieving excellent thermal shrinkage.

[0075] According to one embodiment, the total heat of fusion of the oriented polyester film after the first heat treatment, preheating treatment, and second heat treatment can increase. In particular, after the second heat treatment, several melting points appear that are higher than those before the heat treatment. As a result, it is noteworthy that crystallization begins with the preheating treatment, but the crystallinity can be further enhanced after the second heat treatment.

[0076] Furthermore, the total heat of fusion after the first heat treatment (H 1T ) the total heat of fusion after the second heat treatment (H 2T ) ratio (H 1T / H 2T ) may be 0.1 or greater, for example, 0.1-10.0, 0.1-9.5, 0.1-9.0, 0.2-8.5, 0.2-8.0, 0.3-7.0, 0.3-6.0, 0.3-5.0, 0.3-4.0, 0.3-3.8, 0.3-3.5, or 0.3-3.0.

[0077] Furthermore, the second melting point (T m2 The second heat of fusion (H2) at ) and the second-p melting point (T m2-p ) Heat of fusion of 2-p (H 2-p The ratio to (H2 / H) 2-p) may be 0.1 or greater, for example, 0.1-10.0, 0.2-9.5, 0.3-9.0, 0.3-8.5, 0.3-8.0, 0.3-7.0, 0.3-6.0, 0.3-5.0, 0.3-4.0, 0.3-3.8, 0.3-3.5, 0.3-3.3, 0.3-3.2, 0.35-3.0, 0.35-2.8, or 0.35-2.5.

[0078] Second melting point (T m2 The second heat of fusion (H2) at ) and the second-p melting point (T m2-p ) Heat of fusion of 2-p (H 2-p The ratio to (H2 / H) 2-p When the above range is satisfied, it is possible to maximize crystallinity while simultaneously satisfying excellent thermal shrinkage.

[0079] Furthermore, this oriented polyester film can have a thermal shrinkage rate of 40% or more when represented by the following formula 1-1.

[0080]

number

[0081] In Equation 1-1, L 25 L is the initial length in the transverse direction (TD) of the oriented polyester film sample at 25°C. 80 This is the transverse (TD) length of the oriented polyester film sample after immersion in 80°C water for 10 seconds.

[0082] Specifically, the oriented polyester film may have a heat shrinkage rate of 40% or more, more specifically 42% or more, 44% or more, 46% or more, 48% or more, 50% or more, 52% or more, 55% or more, or 60% or more in the main shrinkage direction represented by the above formula 1-1. For example, the heat shrinkage rate at 80°C in the main shrinkage direction may be 40-70%, 41-65%, 42-60%, 43-60%, 44-58%, or 45-56%.

[0083] Furthermore, this oriented polyester film can have a thermal shrinkage rate of 50% or more when represented by the following formula 1-2.

[0084]

number

[0085] In equation 1-2, L 25 L is the initial length in the transverse direction (TD) of the oriented polyester film sample at 25°C. 90 This is the transverse (TD) length of the oriented polyester film sample after immersion in 90°C water for 10 seconds.

[0086] Specifically, the oriented polyester film may have a heat shrinkage rate of 50% or more, more specifically, 51% or more, 52% or more, 54% or more, 56% or more, 60% or more, 63% or more, or 65% or more in the main shrinkage direction represented by the above formula 1-2. For example, the heat shrinkage rate at 90°C in the main shrinkage direction may be 50-80%, 51-80%, 52-80%, 53-79%, 54-79%, or 55-78%.

[0087] Furthermore, when the polyester label containing this oriented polyester film is applied to plastic containers, particularly polyethylene terephthalate (PET) containers, the crystalline fraction may be 30% or more.

[0088] According to one embodiment, there is provided an oriented polyester film containing a polyester resin in which a diol component and a dicarboxylic acid component are polymerized. When the crystallinity of the polyester oriented film is evaluated by passing a mixture sample, which is obtained by mixing an oriented polyester film sample, obtained by subjecting the oriented polyester film to a first heat treatment at 70°C, a preliminary heat treatment at 160°C and then cutting it into 1 cm × 1 cm pieces, with a polyethylene terephthalate (PET) sample obtained by passing a polyethylene terephthalate (PET) container through a 12.5 mm mesh sieve in a weight ratio of 3:97, heating the mixture sample at 195°C for 90 minutes, and passing the heat-treated mixture sample through the sieve, the crystallinity fraction represented by the following formula 2 is 30% or more.

[0089] [Formula 2] Crystallinity fraction (%) = (F T / F m ) × 100 In formula 2, F T is the ratio ((S s ) / M T ) × 100, %) of the weight (S s ) of the sample that passed through the 12.5 mm mesh sieve among the heat-treated mixture sample to the total weight (M T ) of the heat-treated mixture sample, and F m is the ratio ((C s ) / M T ) × 100, %) of the weight (C s ) of the aggregated sample remaining on the 12.5 mm mesh sieve among the heat-treated mixture sample to the total weight (M T ) of the heat-treated mixture sample.

[0090] Also, the aggregated sample remaining on the 12.5 mm mesh sieve among the heat-treated mixture sample may be defined as an oriented polyester film sample (aggregated sample) that was melted together with the PET sample through the heat treatment.

[0091] The heat-treated mixed sample that passed through a 12.5 mm mesh sieve may be defined as an oriented polyester film sample separated from the PET sample after heat treatment.

[0092] For example, the crystal fraction expressed by the above formula 2 may be 40% or more, 45% or more, 47% or more, 50% or more, 52% or more, 60% or more, 65% or more, 67% or more, 70% or more, 80% or more, 90% or more, 95% or more, or 100%.

[0093] The oriented polyester film sample may be cut after the first heat treatment and the preheat treatment. That is, the oriented polyester film sample may be cut after the preheat treatment and before the second heat treatment.

[0094] The crystal fraction expressed by equation 2 above can serve as an indicator for evaluating regenerative potential and the efficiency of the regeneration process.

[0095] Specifically, if the crystal fraction meets or exceeds the aforementioned range, it can be said that the recyclability and regeneration process efficiency are excellent.

[0096] Specifically, the oriented polyester film according to one embodiment has excellent heat shrinkability and high crystallinity, making it advantageously usable as a heat-shrinkable film for packaging and / or labels for plastic containers. In particular, the oriented polyester film according to the present invention, after being subjected to a first heat treatment and a second heat treatment (or a second heat treatment after preheating), has crystallinity equivalent to or comparable to that of a highly crystalline plastic container (e.g., a PET bottle) (specifically, it has crystallinity equivalent to or comparable to that of polyethylene terephthalate (PET), a component of PET bottles). Since melting together with the plastic container does not occur in the recycling process of used plastic containers, the recycling process of used plastic containers can be carried out without the step of separating (removing) the oriented polyester film from the used plastic container. Therefore, the present invention can improve the efficiency of the recycling process of used plastic containers compared to the prior art.

[0097] Furthermore, the polyester resin contained in the oriented polyester film according to the present invention may be a polyester resin in which a diol component and a dicarboxylic acid component are polymerized.

[0098] According to the present invention, the diol component may be a known diol component. Specifically, the diol component may be bis(2-hydroxyethyl) terephthalate, isosorbide, neopentyl glycol, ethylene glycol, cyclohexanedimethanol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol It may contain at least one selected from the group consisting of ol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, 4-(hydroxymethyl)cyclohexylmethyl-4-(hydroxymethyl)cyclohexanecarboxylate (CHDM derivative), 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol (CHDM derivative), regenerated cyclohexanedimethanol, regenerated ethylene glycol, regenerated bis(2-hydroxyethyl)terephthalate, and regenerated diethylene glycol. Preferably, considering the crystallinity, heat shrinkage, and economic efficiency of the oriented polyester film, the diol component may include two or more (specifically, three or more, four or more, or five or more) selected from the group consisting of bis(2-hydroxyethyl) terephthalate, isosorbide, ethylene glycol, cyclohexanedimethanol, neopentyl glycol, diethylene glycol, 4-(hydroxymethyl)cyclohexylmethyl-4-(hydroxymethyl)cyclohexanecarboxylate, 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol, and regenerated bis(2-hydroxyethyl) terephthalate.

[0099] For example, the diol component may include ethylene glycol and at least one (specifically, two or more, three or more, or four or more) selected from the group consisting of bis(2-hydroxyethyl) terephthalate, isosorbide, cyclohexanedimethanol, neopentyl glycol, diethylene glycol, 4-(hydroxymethyl)cyclohexylmethyl-4-(hydroxymethyl)cyclohexanecarboxylate, 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol, and regenerated bis(2-hydroxyethyl) terephthalate as a comonomer.

[0100] When the diol component contains ethylene glycol and a comonomer, the amounts of these components are not particularly limited, but the amount of ethylene glycol may be 10-100% by weight, 15-90% by weight, 20-85% by weight, 30-85% by weight, or 50-85% by weight relative to the total weight of the diol component, and the amount of comonomer may be greater than 0-90% by weight, greater than 0-85% by weight, 1-90% by weight, 1-50% by weight, 2-50% by weight, 10-85% by weight, 15-80% by weight, 15-70% by weight, or 15-50% by weight. In particular, when diethylene glycol is used as a comonomer, the amount of diethylene glycol may be 0-50% by weight, 1-50% by weight, 2-50% by weight, 3-45% by weight, 4-40% by weight, or 5-35% by weight relative to the total weight of the diol component. Therefore, the polyester resin according to the present invention may contain diethylene glycol-derived structural units in an amount of 0-50% by weight, 1-50% by weight, 2-50% by weight, 3-45% by weight, 4-40% by weight, or 5-35% by weight relative to the total weight of the polyester resin.

[0101] According to the present invention, the dicarboxylic acid component may be a known dicarboxylic acid component. Specifically, the dicarboxylic acid component may include at least one selected from the group consisting of isophthalic acid, terephthalic acid, dimethyl isophthalate, phthalic acid, dimethyl phthalate, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, dimethyl 2,6-naphthalenedicarboxylate, diphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, dimethyl 1,4-cyclohexanedicarboxylate, dimethyl 1,3-cyclohexanedicarboxylate, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, glutaric acid, azelaic acid, regenerated isophthalic acid, regenerated terephthalic acid, regenerated dimethyl isophthalate, and regenerated dimethyl phthalate. Preferably, considering the crystallinity and heat shrinkage of the oriented polyester film, the dicarboxylic acid component may include at least one selected from the group consisting of isophthalic acid, terephthalic acid, dimethyl phthalate, and dimethyl isophthalate.

[0102] According to the present invention, the polyester resin may have an intrinsic viscosity (IV) of 0.5 to 1.2 dl / g at 35°C, specifically 0.52 to 1.15 dl / g, 0.55 to 1.13 dl / g, 0.58 to 1.1 dl / g, 0.6 to 0.9 dl / g, 0.62 to 0.88 dl / g, 0.65 to 0.85 dl / g, 0.68 to 0.83 dl / g, or 0.7 to 0.8 dl / g. If the intrinsic viscosity is within the above range, the processability of the polyester resin can be said to be ensured. (Method for preparing oriented polyester film) According to one embodiment, a method for preparing the aforementioned oriented polyester film is provided.

[0103] In detail, a method for preparing an oriented polyester film according to one embodiment includes polymerizing a diol component and a dicarboxylic acid component to prepare a polyester resin (S-1), preparing an oriented polyester sheet from the polyester resin (S-2), and heat-fixing the oriented sheet (S-3), wherein when the film is subjected to a first heat treatment and a second heat treatment and subsequently analyzed by differential scanning calorimetry (DSC), a first melting point (Tm1) and a second melting point (Tm2) appear, and the ratio (H2 / H1) of the second heat of fusion (H2) at the second melting point (Tm2) to the first heat of fusion (H1) at the first melting point (Tm1) is 0.1 or greater.

[0104] In addition, a method for preparing an oriented polyester film according to one embodiment includes polymerizing a diol component and a dicarboxylic acid component to prepare a polyester resin (S-1), preparing an oriented polyester sheet from the polyester resin (S-2), and heat-fixing the oriented sheet (S-3). The oriented polyester film sample obtained by subjecting the oriented polyester film to a first heat treatment at 70°C and a preheat treatment at 160°C, and then cutting it into 1cm × 1cm pieces, is mixed with a polyethylene terephthalate (PET) sample obtained by passing a polyethylene terephthalate (PET) container through a 12.5mm mesh sieve in a weight ratio of 3:97. This mixed sample is heat-treated at 195°C for 90 minutes. When the crystallinity of the polyester oriented film is evaluated by passing the heat-treated mixed sample through the sieve, the crystallinity fraction expressed by the above formula 2 is 30% or more.

[0105] This will be explained in detail below.

[0106] Step (S-1): Preparation of polyester resin In step (S-1), a polyester resin (copolymer) is prepared by polymerizing the diol component and the dicarboxylic acid component.

[0107] The diol and dicarboxylic acid components used in polymerization are the same as those mentioned earlier, so their explanation will be omitted.

[0108] Polymerization of diol components and dicarboxylic acid components can be carried out by conventionally known methods (e.g., liquid-phase polymerization, solid-phase polymerization, etc.). Batch reactors or continuous reactors can be used for the polymerization reaction. Specifically, the polymerization reaction may include an esterification reaction (transesterification reaction) to prepare an oligomer by reacting the diol component with the dicarboxylic acid component, and a polycondensation reaction of this oligomer.

[0109] The temperature during the esterification reaction is not particularly limited, but considering the physical properties of the polyester resin and oriented polyester film, it may be 230-270°C, 235-268°C, 240-265°C, or 240-260°C. In addition, the length of time during the esterification reaction is not particularly limited, but may be 1-24 hours, 2-22 hours, 3-20 hours, or 4-18 hours. In addition, the pressure during the esterification reaction is not particularly limited, but may be 0-5.0 kgf / cm². 2 , 0.1~4.5 kgf / cm² 2 , 0.1~4.0 kgf / cm² 2 , or 0.1~3.0 kgf / cm² 2 That's fine.

[0110] The temperature during the polycondensation reaction is not particularly limited, but considering the physical properties of the polyester resin and the oriented polyester film, it may be 245-290°C, 250-285°C, 255-280°C, or 255-270°C. In addition, the length of time for carrying out the polycondensation reaction is not particularly limited, but may be 1-24 hours, 2-24 hours, 5-22 hours, or 7-20 hours.

[0111] Furthermore, additives containing at least one selected from the group consisting of catalysts, stabilizers, colorants, crystallizers, antioxidants, and branching agents can be used in the polymerization reaction.

[0112] The catalyst is not particularly limited, but may specifically be sodium and magnesium methylates; acetates, borates, fatty acid salts and carbonates of Zn, Cd, Mn, Co, Ca, and Ba; or oxides or hydrates of Mg, Pb, Mn, Ti, Zn, Sb, and Ge. For example, the catalyst may be tetraethyl titanate, acetyl tripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, octylene glycol titanate, triethanolamine titanate, acetyl acetonate titanate, ethyl acetoacetate titanate, isostearyl titanate, titanium dioxide, germanium dioxide, germanium tetrachloride, germanium ethylene glycoside, germanium acetate, or a combination thereof.

[0113] The stabilizer is not particularly limited, but phosphorus compounds such as phosphoric acid, trimethyl phosphate, and triethyl phosphate can be used.

[0114] The colorants are not particularly limited, but organic compounds such as cobalt compounds, anthraquinone compounds, perinone compounds, azo compounds, and methine compounds (for example, cobalt acetate, cobalt propionate, Clariant's Polysynthren Blue RLS toner, and Clariant's Solvaperm Red BB toner) can be used.

[0115] The crystallizing agent is not particularly limited, but nucleating agents, UV absorbers, polyolefin resins, polyamide resins, etc., can be used.

[0116] The antioxidant is not particularly limited, but hindered phenol compounds, phosphite compounds, thioether compounds, etc., can be used.

[0117] The branching agent is not particularly limited, but trimellitic anhydride, trimethylolpropane, trimellitic anhydride, etc., can be used.

[0118] Step (S-2): Preparation of oriented polyester sheet In step (S-2), an oriented polyester sheet is prepared from the polyester resin obtained in step (S-1). The oriented sheet can be prepared by conventionally known methods. Specifically, the oriented sheet can be prepared using a melt casting step, a uniaxial or biaxial stretching step, and / or a heat setting step of the polyester resin.

[0119] The melt casting step of the polyester resin can be carried out using an extruder. In such cases, the melt temperature is not particularly limited, but may be 180-310°C, 200-310°C, 230-310°C, 240-300°C, or 250-290°C. An unoriented sheet can be obtained through such a step, and the unoriented sheet thus obtained can be sent to the stretching step. The unoriented sheet may be preheated to a predetermined temperature (e.g., 90-120°C) before proceeding to the stretching step.

[0120] The uniaxial or biaxial stretching step may be carried out by stretching the unoriented sheet obtained through the molten casting step in the longitudinal (MD), transverse (TD), or both directions. Longitudinal stretching can be carried out at 55-180°C or 60-170°C with a stretch ratio of 1-5 times or 1.1-4.5 times. In addition, transverse stretching can be carried out at 55-180°C or 60-170°C with a stretch ratio of 1.5-6 times or 2.5-5.5 times.

[0121] Oriented polyester films prepared through such stretching steps may have a heat shrinkage rate of 40% or more, more specifically 42% or more, 44% or more, 46% or more, 48% or more, 50% or more, 52% or more, 55% or more, or 60% or more at 80°C in the main shrinkage direction. For example, the heat shrinkage rate at 80°C in the main shrinkage direction may be 40-70%, 41-65%, 42-60%, 43-60%, 44-58%, or 45-56%.

[0122] In addition, the oriented polyester film prepared through such a stretching step may have a heat shrinkage rate of 50% or more at 90°C in the main shrinkage direction, specifically 51% or more, 52% or more, 54% or more, 56% or more, 60% or more, 63% or more, or 65% or more. For example, the heat shrinkage rate at 90°C in the main shrinkage direction may be 50-80%, 51-80%, 52-80%, 53-79%, 54-79%, or 55-78%.

[0123] Step (S-3): Heat fixation In step (S-3), the orientation sheet obtained in step (S-2) is heat-fixed. The temperature at which the orientation sheet is heat-fixed is not particularly limited, but may be equal to or higher than the temperature at which it was heat-fixed in the stretching step. Specifically, the heat-fixing temperature may be 60-200°C, 65-190°C, 65-180°C, or 65-170°C. When the heat-fixing temperature is within the above range, an orientation polyester film with high crystallinity and high mechanical strength can be prepared.

[0124] Furthermore, this oriented polyester film may be subjected to further heat treatment. The heat treatment may be carried out two or more times.

[0125] Step (S-4): First heat treatment Step (S-4) is a step in which the oriented polyester film obtained in step (S-3) is subjected to a first heat treatment.

[0126] The first heat treatment temperature is not particularly limited, but may be 60-105°C, specifically 62-104°C, 62-103°C, 65-102°C, 68-100°C, 70-100°C, 70-98°C, 70-97°C, or 70-96°C. For example, the first heat treatment may be carried out by immersing the oriented polyester film prepared in step (S-3) in hot water having the aforementioned temperature range for 1 minute or less, specifically 50 seconds or less, 40 seconds or less, 30 seconds or less, 20 seconds or less, specifically 5 seconds to 60 seconds, 5 seconds to 50 seconds, 5 seconds to 40 seconds, 5 seconds to 30 seconds, 5 seconds to 20 seconds, or 5 seconds to 15 seconds.

[0127] Step (S-5): Second heat treatment Step (S-5) is a step of subjecting the oriented polyester film that has undergone the first heat treatment in step (S-4) to a second heat treatment. The temperature of the second heat treatment is not particularly limited, but may be 140 to 220°C, specifically 141 to 219°C, 142 to 218°C, 143 to 217°C, 144 to 216°C, 145 to 215°C, 145 to 214°C, 146 to 213°C, or 150 to 210°C. For example, the second heat treatment may be carried out by placing the oriented polyester film subjected to the first heat treatment in step (S-4) into an oven and applying the aforementioned temperature range, leaving it for 4 hours or less, specifically 200 minutes or less, 180 minutes or less, 150 minutes or less, 120 minutes or less, 100 minutes or less, for example, 10 to 200 minutes, 10 to 180 minutes, 20 to 150 minutes, 30 to 120 minutes, 40 to 120 minutes, 60 to 120 minutes, and 70 to 100 minutes.

[0128] Furthermore, according to one embodiment, step (S-5) may further include a step of subjecting the oriented polyester film that has undergone the first heat treatment in step (S-4) to a preheat treatment prior to the second heat treatment.

[0129] Specifically, the second heat treatment may be performed after preheating the oriented polyester film subjected to the first heat treatment.

[0130] The preheating treatment may be carried out in the same or similar temperature range as the second heat treatment. For example, the preheating treatment may be carried out at a temperature of 140-220°C, specifically 141-219°C, 142-218°C, 143-217°C, 144-216°C, 145-215°C, 145-214°C, 146-213°C, or 150-210°C for 1-30 minutes, 1-20 minutes, 5-30 minutes, 5-25 minutes, 5-20 minutes, 5-15 minutes, 6-25 minutes, 6-20 minutes, 6-15 minutes, or 6-13 minutes.

[0131] For example, step (S-5) may include preheating the orientation polyester film that has been subjected to the first heat treatment at 140-220°C for 1-30 minutes, cooling it to room temperature for 1-30 minutes, and then subjecting the orientation polyester film that has been subjected to the preheat treatment to a second heat treatment at 140-220°C for 10-200 minutes.

[0132] In addition, step (S-5) may include a step in which the oriented polyester film that has been subjected to the first heat treatment is preheated at 150-210°C for 1-30 minutes, cooled to room temperature for 1-30 minutes, and then subjected to a second heat treatment at 150-210°C for 10-180 minutes.

[0133] In the present invention, the oriented polyester film obtained through the stretching step, when heat-treated as described above, can have an excellent thermal shrinkage rate and highly controllable crystallinity.

[0134] Specifically, the oriented polyester film can be shrunk through a first heat treatment, and the crystallinity of the oriented polyester film can be strengthened through a second heat treatment.

[0135] Furthermore, if the preheating treatment is performed after the first heat treatment and before the second heat treatment, the oriented polyester film that has shrunk due to the first heat treatment will crystallize. The crystallinity of this oriented polyester film can be maximized to an optimal range through the second heat treatment, thereby further enhancing the efficiency of the regeneration process.

[0136] If the heat treatment of the oriented polyester film is performed only once, the crystallinity of the film will not increase to the desired level. Therefore, as in the present invention, it is preferable that the heat treatment of the oriented polyester film be performed as a first and second heat treatment (twice), or multiple times (two or more times) including a first, preliminary, and second heat treatment.

[0137] Furthermore, in the oriented polyester film prepared through the steps described above according to the present invention, when the film is subjected to a first heat treatment and a second heat treatment and then analyzed by differential scanning calorimetry (DSC), a first melting point (Tm1) and a second melting point (Tm2) appear. m2 The second heat of fusion (H2) at ) is the first melting point (T m1 When the ratio (H2 / H1) to the first heat of fusion (H1) in ) satisfies a specific range, it is possible to achieve extremely high crystallinity along with excellent thermal shrinkage, heat resistance, and durability.

[0138] The heating temperatures and times for the first and second heating treatments are as described above.

[0139] In addition, the temperature and time of the preheating treatment described below are as stated above.

[0140] According to another embodiment, when differential scanning calorimetry (DSC) analysis is performed after the first heat treatment, after the preheating treatment prior to the second heat treatment, and after the second heat treatment, the first melting point (T) is as described above. m1 ), 2nd-p melting point (T m2-p ) and the second melting point (T m2 ) appears, and the second melting point (T m2 The second heat of fusion (H2) at ) is the first melting point (T m1 The ratio (H2 / H1) to the first heat of fusion (H1) at ) and / or the second melting point (T m2 The second heat of fusion (H2) at ) and the second-p melting point (T m2-p ) Heat of fusion of 2-p (H 2-p The ratio to (H2 / H)2-p The material satisfies a specific range. As a result, crystallinity can be maximized. Such high crystallinity allows for the recycling process of used plastic containers without separating the oriented polyester film (for example, it is possible to recycle plastic containers with the oriented polyester film still attached). Consequently, the present invention can improve the efficiency of the recycling process compared to the prior art.

[0141] (Goods) The present invention provides an article comprising an oriented polyester film.

[0142] According to one embodiment, an article is provided comprising an oriented polyester film containing a polyester resin, wherein the oriented polyester film contains a polyester resin in which a diol component and a dicarboxylic acid component are polymerized, and when the film is subjected to a first heat treatment and a second heat treatment and subsequently analyzed by differential scanning calorimetry (DSC), a first melting point (Tm1) and a second melting point (Tm2) appear, and the ratio (H2 / H1) of the second heat of fusion (H2) at the second melting point (Tm2) to the first heat of fusion (H1) at the first melting point (Tm1) is 0.1 or greater.

[0143] Furthermore, the article may include an oriented polyester film (polyester film) prepared by the first heat treatment and the second heat treatment, or the first heat treatment, preheating treatment and the second heat treatment, as described above.

[0144] The article may also be obtained by molding polyester resin using molding methods such as extrusion and injection molding. The article may be a film (or sheet) or component used in the fields of automobiles, electrical and electronic engineering.

[0145] Furthermore, the article may include labels or cap seals for various containers, such as plastic containers, or packaging materials.

[0146] The present invention will be described in more detail below with reference to embodiments. However, the examples described herein are provided for illustrative purposes only, and the present invention is not limited to these examples.

[0147] [Mode of the invention] [Example 1] (1) Preparation of polyester resin (copolymer) A water-coolable 10-liter reactor equipped with a column and condenser was packed with terephthalic acid (TPA, 7,693.0 g), isosorbide (ISB, 96.7 g), ethylene glycol (EG, 2,601.3 g), 1,4-cyclohexanedimethanol (CHDM, 1,557.1 g), diethylene glycol (DEG, 1,213.7 g), Ge catalyst (GeO2, 1.0 g), Ti catalyst (1.0 g), phosphoric acid (1.5 g), blue toner (0.01 g), and red toner (0.005 g). Next, the reactor temperature was raised to 265°C, and then the reactor was operated at 265°C and a pressure of 2 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a transparent resulting material.

[0148] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 270°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.77 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0149] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented sheet was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0150] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0151] Subsequently, the oriented polyester film was subjected to a first heat treatment, during which it was immersed in 70°C water for 10 seconds to induce shrinkage. Next, to enhance the crystallinity of the oriented polyester film, the polyester oriented film subjected to the first heat treatment was preheated by placing it in a 160°C oven for 10 minutes and then cooled at room temperature for 30 minutes. Subsequently, the oriented polyester film subjected to the preheat treatment was subjected to a second heat treatment by placing it in a 160°C oven for 90 minutes.

[0152] [Example 2] (1) Preparation of polyester resin (copolymer) A water-cooled 10-liter reactor equipped with a column and condenser was packed with terephthalic acid (TPA, 7,663.2g), ethylene glycol (EG, 3,345.5g), 1,4-cyclohexanedimethanol (CHDM, 1,255.7g), neopentyl glycol (NPG, 106.7g), diethylene glycol (DEG, 978.7g), cyclohexanedimethanol derivative (CHDM derivative, 247.4g), Ti catalyst (1.0g), blue toner (0.01g), and red toner (0.01g). Next, the reactor temperature was raised to 255°C, and then the reactor was operated at 255°C and a pressure of 1 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a clear resulting substance.

[0153] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 285°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.65 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0154] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented film was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0155] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0156] Subsequently, the oriented polyester film was subjected to a first heat treatment, during which it was immersed in 90°C water for 10 seconds to induce shrinkage. Next, to enhance the crystallinity of the oriented polyester film, the polyester oriented film subjected to the first heat treatment was preheated by placing it in a 175°C oven for 10 minutes and then cooled at room temperature for 30 minutes. Subsequently, the oriented polyester film subjected to the preheat treatment was subjected to a second heat treatment by placing it in a 175°C oven for 90 minutes.

[0157] [Example 3] (1) Preparation of polyester resin (copolymer) A water-coolable 10-liter reactor equipped with a column and condenser was packed with recycled bis(2-hydroxyethyl) terephthalate (r-BHET, 1,202.9 g), terephthalic acid (TPA, 7,075.2 g), ethylene glycol (EG, 3,488.9 g), 1,4-cyclohexanedimethanol (CHDM, 1,363.9 g), diethylene glycol (DEG, 1,063.0 g), Ti catalyst (1.0 g), blue toner (0.02 g), and red toner (0.01 g). The reactor temperature was then raised to 255°C, followed by heating at 255°C and a pressure of 0.5 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a clear resulting substance.

[0158] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 285°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.70 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0159] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented sheet was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0160] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0161] Subsequently, the oriented polyester film was subjected to a first heat treatment, during which it was immersed in 95°C water for 10 seconds to induce shrinkage. Next, to enhance the crystallinity of the oriented polyester film, the polyester oriented film subjected to the first heat treatment was preheated by placing it in a 155°C oven for 10 minutes and then cooled at room temperature for 30 minutes. Subsequently, the oriented polyester film subjected to the preheat treatment was subjected to a second heat treatment by placing it in a 155°C oven for 90 minutes.

[0162] [Example 4] (1) Preparation of polyester resin (copolymer) A water-coolable 10-liter reactor equipped with a column and condenser was packed with terephthalic acid (TPA, 7,918.3 g), ethylene glycol (EG, 4,080.5 g), 1,4-cyclohexanedimethanol (CHDM, 1,068.5 g), diethylene glycol (DEG, 832.8 g), Ge catalyst (GeO2, 1.0 g), blue toner (0.05 g), and red toner (0.02 g). Next, the reactor temperature was raised to 260°C, and then the reactor was operated at 260°C and a pressure of 1 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a clear resulting substance.

[0163] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 275°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.78 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0164] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented film was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0165] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0166] Subsequently, the oriented polyester film was subjected to a first heat treatment, during which it was immersed in 95°C water for 10 seconds to induce shrinkage. Next, to enhance the crystallinity of the oriented polyester film, the polyester oriented film subjected to the first heat treatment was preheated by placing it in a 165°C oven for 10 minutes and then cooled at room temperature for 30 minutes. Subsequently, the oriented polyester film subjected to the preheat treatment was subjected to a second heat treatment by placing it in a 165°C oven for 90 minutes.

[0167] [Example 5] (1) Preparation of polyester resin (copolymer) A water-coolable 10-liter reactor equipped with a column and condenser was packed with terephthalic acid (TPA, 7,878.5 g), isosorbide (ISB, 494.9 g), ethylene glycol (EG, 4,076.7 g), 1,4-cyclohexanedimethanol (CHDM, 1,139.1 g), diethylene glycol (DEG, 887.8 g), Mn catalyst (Mn(II) acetate tetrahydrate, 1.5 g), Sb catalyst (Sb2O3, 1.8 g), and cobalt acetate (0.8 g). Next, the reactor temperature was raised to 240°C, and then the reactor was operated at 240°C and a pressure of 0.1 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a clear resulting substance.

[0168] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 255°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.85 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0169] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented film was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0170] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0171] Subsequently, the oriented polyester film was subjected to a first heat treatment, during which it was immersed in 95°C water for 10 seconds to induce shrinkage. Next, to enhance the crystallinity of the oriented polyester film, the polyester oriented film subjected to the first heat treatment was preheated by placing it in a 175°C oven for 10 minutes and then cooled at room temperature for 30 minutes. Subsequently, the oriented polyester film subjected to the preheat treatment was subjected to a second heat treatment by placing it in a 175°C oven for 90 minutes.

[0172] [Example 6] (1) Preparation of polyester resin (copolymer) A water-cooled 10-liter reactor equipped with a column and condenser was packed with terephthalic acid (TPA, 8,279.3g), ethylene glycol (EG, 4,432.3g), neopentyl glycol (NPG, 864.5g), Ge catalyst (GeO2, 1.0g), cobalt acetate (0.4g), blue toner (0.03g), and red toner (0.01g). Next, the reactor temperature was raised to 250°C, and then the reactor was operated at 250°C and a pressure of 1 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a clear resulting substance.

[0173] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 285°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.70 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0174] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented film was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0175] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0176] Subsequently, the oriented polyester film was subjected to a first heat treatment, during which it was immersed in 95°C water for 10 seconds to induce shrinkage. Next, to enhance the crystallinity of the oriented polyester film, the polyester oriented film subjected to the first heat treatment was preheated by placing it in a 160°C oven for 10 minutes and then cooled at room temperature for 30 minutes. Subsequently, the oriented polyester film subjected to the preheat treatment was subjected to a second heat treatment by placing it in a 160°C oven for 90 minutes.

[0177] [Example 7] (1) Preparation of polyester resin (copolymer) A water-coolable 10-liter reactor equipped with a column and condenser was packed with recycled bis(2-hydroxyethyl) terephthalate (r-BHET, 2,288.5g), terephthalic acid (TPA, 5,982.5g), ethylene glycol (EG, 739.3g), 1,4-cyclohexanedimethanol (CHDM, 1,441.6g), neopentyl glycol (NPG, 1,301.4g), diethylene glycol (DEG, 1,123.6g), Ge catalyst (GeO2, 1.0g), blue toner (0.03g), and red toner (0.01g). Next, the reactor temperature was raised to 265°C, and then the reactor was operated at 265°C and a pressure of 2 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a clear resulting substance.

[0178] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 270°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.78 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0179] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented film was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0180] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0181] Subsequently, the oriented polyester film was subjected to a first heat treatment, during which it was immersed in 100°C water for 10 seconds in order to induce shrinkage. Next, to enhance the crystallinity of the oriented polyester film, the polyester oriented film subjected to the first heat treatment was preheated by placing it in a 210°C oven for 10 minutes and then cooled at room temperature for 30 minutes. Subsequently, the oriented polyester film subjected to the preheat treatment was subjected to a second heat treatment by placing it in a 210°C oven for 90 minutes.

[0182] [Example 8] (1) Preparation of polyester resin (copolymer) A water-coolable 10-liter reactor equipped with a column and condenser was packed with recycled bis(2-hydroxyethyl) terephthalate (r-BHET, 2,509.9 g), terephthalic acid (TPA, 6,561.3 g), ethylene glycol (EG, 3,281.5 g), 1,4-cyclohexanedimethanol (CHDM, 790.5 g), diethylene glycol (DEG, 616.1 g), Ti catalyst (1.0 g), blue toner (0.01 g), and red toner (0.01 g). The reactor temperature was then raised to 263°C, followed by heating at 263°C and a pressure of 1 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a clear resulting substance.

[0183] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 275°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.70 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0184] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented film was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0185] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0186] Subsequently, the oriented polyester film was subjected to a first heat treatment, during which it was immersed in 80°C water for 10 seconds to induce shrinkage. Next, to enhance the crystallinity of the oriented polyester film, the polyester oriented film subjected to the first heat treatment was preheated by placing it in a 170°C oven for 10 minutes and then cooled at room temperature for 30 minutes. Subsequently, the oriented polyester film subjected to the preheat treatment was subjected to a second heat treatment by placing it in a 170°C oven for 90 minutes.

[0187] (Comparative Example 1) (1) Preparation of polyester resin (copolymer) A water-coolable 10-liter reactor equipped with a column and condenser was packed with regenerated bis(2-hydroxyethyl) terephthalate (r-BHET, 2,256.8 g), terephthalic acid (TPA, 5,899.6 g), ethylene glycol (EG, 824.5 g), 1,4-cyclohexanedimethanol (CHDM, 2,487.8 g), diethylene glycol (DEG, 1,939.0 g), Ge catalyst (GeO2, 1.0 g), blue toner (0.01 g), and red toner (0.01 g). Next, the reactor temperature was raised to 273°C, and then the reactor was operated at 273°C and a pressure of 0.5 kgf / cm². 2 An esterification reaction (ES) was carried out below to obtain a clear resulting substance.

[0188] Next, the resulting material was transferred to a polycondensation reactor, and a polycondensation reaction (PA) was carried out at 285°C, during which the pressure in the polycondensation reactor was maintained at a pressure lower than atmospheric pressure. When the intrinsic viscosity (IV) of the mixture in the polycondensation reactor reached 0.80 dl / g, the mixture was discharged from the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to have an average weight of approximately 12-14 mg to prepare polyester resin (copolymer) chips.

[0189] (2) Preparation of oriented polyester sheets Polyester resin chips were fed into an extruder, melt-extruded at a temperature of 180-310°C, and then cast at a temperature of 20-70°C to prepare an unoriented polyester sheet. Subsequently, this unoriented film was heated to 75-90°C and oriented five times in the transverse direction (TD) to prepare an oriented polyester sheet.

[0190] (3) Heat fixation An oriented polyester sheet was heat-set at 60-220°C to prepare an oriented polyester film with a thickness of 50 μm.

[0191] Subsequently, the oriented polyester film was subjected to a first heat treatment by immersing it in 110°C water for 10 seconds. Next, the oriented polyester film subjected to the first heat treatment was subjected to a second heat treatment by placing it in a 225°C oven for 30 minutes.

[0192] (Test Example 1) The oriented polyester films subjected to the first heat treatment, preheat treatment, and second heat treatment in Examples 1-8 and Comparative Example 1 were analyzed by differential scanning calorimetry (DSC) to determine their melting points (T m We determined whether or not the following appeared. The results are shown in Table 1 and Figure 1 (Example 6) below. DSC analysis of the oriented polyester film was performed as follows.

[0193] DSC analyzer: A Mettler Toledo DSC1 model was used.

[0194] Sample preparation: Approximately 6-10 mg of oriented polyester film subjected to the first and second heat treatments, or the first, preliminary, and second heat treatments, was taken and placed in an aluminum pan.

[0195] Scanning conditions: The sample was heated from room temperature to 280°C at a rate of 10°C / min, followed by annealing at 280°C for 3 minutes to obtain the DSC curve.

[0196] Determination of the melting point: In the obtained DSC curve, the temperature at which an endothermic peak appeared during the heating procedure was defined as the melting point.

[0197] As can be seen from Figure 1, the oriented polyester film of Example 6 shows different results after the first heat treatment, preheat treatment, and second heat treatment.

[0198] Specifically, the total heat of fusion of the oriented polyester film of Example 6 after undergoing the first heat treatment, preheating treatment, and second heat treatment increased. In particular, after the second heat treatment, several melting points increased compared to before the heat treatment. As a result, it is noteworthy that crystallization begins with the preheating treatment, but crystallinity can be further enhanced after the second heat treatment.

[0199] (Test Example 2) The heat shrinkage rates of the oriented polyester films subjected to the first heat treatment in Examples 1-8 and Comparative Example 1 were evaluated as follows. The results are shown in Table 1 below.

[0200] Sample preparation: The oriented polyester film was cut into 5cm x 5cm pieces and stored at room temperature (25°C).

[0201] Thermal shrinkage at 80°C: An oriented polyester film sample was immersed in 80°C water for 10 seconds, and the change in length in the transverse direction (TD), which is the primary shrinkage direction, was calculated using the following equation 1-1.

[0202] Thermal shrinkage at 90°C: An oriented polyester film sample was immersed in 90°C water for 10 seconds, and the change in length in the transverse direction (TD), which is the primary shrinkage direction, was calculated using the following equation 1-2.

[0203]

number

[0204] In Equation 1-1, L 25 L is the initial length in the transverse direction (TD) of the oriented polyester film sample at 25°C. 80 This is the transverse (TD) length of the oriented polyester film sample after immersion in 80°C water for 10 seconds.

[0205]

number

[0206] In equation 1-2, L 25 L is the initial length in the transverse direction (TD) of the oriented polyester film sample at 25°C. 90 This is the transverse (TD) length of the oriented polyester film sample after immersion in 90°C water for 10 seconds.

[0207] (Test Example 3) In Examples 1 to 8 and Comparative Example 1, the oriented polyester films, after preheating and before the second heat treatment, were evaluated for recyclability (crystallinity) as follows. The results are shown in Table 1 below.

[0208] Sample preparation: In Examples 1 to 8 and Comparative Example 1, the oriented polyester film was preheated and then cut into 1 cm x 1 cm pieces before the second heat treatment to prepare oriented polyester film samples (flakes).

[0209] In addition, polyethylene terephthalate (PET) containers were crushed using a crusher and passed through a 12.5 mm mesh sieve to prepare PET samples (flakes) of the above size in which polyethylene terephthalate (PET) had been crushed.

[0210] An oriented polyester film sample (flake) and a PET sample (flake) were mixed, and this mixed sample was heat-treated at 195°C for 90 minutes.

[0211] Subsequently, the heat-treated mixed sample (mixed flakes) was passed through a 12.5 mm mesh sieve to obtain the aggregated sample remaining on the sieve. This was defined as the oriented polyester film sample that had been melted together with the PET sample after heat treatment.

[0212] Furthermore, the heat-treated mixed sample (mixed flakes) was passed through a 12.5 mm mesh sieve to obtain the sample that passed through the sieve. This was defined as an oriented polyester film sample separated from the PET sample after heat treatment.

[0213] The weight of each sample was measured, and the crystal fraction (%) expressed by the following equation 2 was calculated. [Formula 2] Crystal fraction (%)=(F T / F m ) × 100 In Equation 2, F T This refers to the weight (S) of the heat-treated mixed sample that passed through a 12.5 mm mesh sieve. s The total weight (M) of the heat-treated mixed sample. T ) ratio ((S s / M T ) × 100, %) and F m This refers to the weight of the aggregated sample remaining on a 12.5 mm mesh sieve from the heat-treated mixed sample (C s The total weight (M) of the heat-treated mixed sample. T ) ratio ((C s / M T ) × 100, %).

[0214] [Table 1]

[0215] Referring to Table 1, the oriented polyester films of Examples 1 to 8 of the present invention have two or more melting points (T m1 , T m2-p , T m2 ), and a second melting point (T) that satisfies a specific range m2 The second heat of fusion (H2) at ) is the first melting point (T m1 The ratio (H2 / H1) to the first heat of fusion (H1) at ) and / or the second melting point (T m2 The second heat of fusion (H2) at ) and the second-p melting point (T m2-p ) Heat of fusion of 2-p (H 2-p The ratio to (H2 / H) 2-p In such oriented polyester films, the temperature-dependent thermal shrinkage rate is high, and the crystal fraction is enhanced, ensuring recyclability.

[0216] In contrast, the oriented polyester film of Comparative Example 1, which had only one melting point, had a significantly lower crystal fraction of 27%.

[0217] Furthermore, in the oriented polyester film of Example 8, the use of a small amount of comonomer (e.g., diethylene glycol) slightly reduced the thermal shrinkage rate.

[0218] Therefore, the oriented polyester film according to the present invention can be advantageously used as a heat-shrinkable film for labels for packaging and / or plastic containers.

[0219] Furthermore, the oriented polyester film according to the present invention has high crystallinity. In the recycling process of used plastic containers, it may be possible to recycle the plastic containers without separating the oriented polyester film (for example, it is possible to recycle plastic containers with the oriented polyester film still attached). Therefore, the recycling process efficiency can be improved compared to the prior art.

Claims

1. An oriented polyester film comprising a polyester resin in which a diol component and a dicarboxylic acid component are polymerized, When the film is subjected to a first heat treatment and a second heat treatment, and then analyzed by differential scanning calorimetry (DSC), the first melting point (Tm １ ) and the second melting point (Tm ２ ) appeared, Second melting point (Tm ２ The second heat of fusion (H) in ) ２ The first melting point (Tm) of ) １ The first heat of fusion (H) in ) １ ) Ratio (H ２ / H １ An oriented polyester film in which the ratio is 0.1 or higher.

2. When the oriented polyester film after the first heat treatment and after the preliminary heat treatment prior to the second heat treatment is analyzed by differential scanning calorimetry (DSC), the second-p melting point (T ｍ２－ｐ ) appears, Second melting point (T ｍ２ The second heat of fusion (H) in ) ２ The second-p melting point (T ｍ２－ｐ ) Heat of fusion of 2-p (H ２－ｐ ) Ratio (H ２ / H ２－ｐ The orientation polyester film according to claim 1, wherein the ratio of the ratios is 0.1 or greater.

3. After the first heat treatment, one or more first melting points (T ｍ１ ) appears, and the total heat of fusion (H １Ｔ The orientation polyester film according to claim 1, wherein the amount is 1.0 J / g or more.

4. After the second heat treatment, one or more second melting points (T ｍ２ ) appears, and the total heat of fusion (H ２Ｔ The orientation polyester film according to claim 1, wherein the amount is 1.0 J / g or more.

5. Total heat of fusion after the first heat treatment (H １Ｔ ) the total heat of fusion after the second heat treatment (H ２Ｔ ) Ratio (H １Ｔ / H ２Ｔ The orientation polyester film according to claim 1, wherein the ratio of the ratios is 0.1 or greater.

6. After the second heat treatment, the second melting point (T ｍ２ The oriented polyester film according to claim 1, wherein the temperature is 150°C to 230°C and is crystalline.

7. An oriented polyester film comprising a polyester resin in which a diol component and a dicarboxylic acid component are polymerized, The oriented polyester film sample obtained by subjecting the oriented polyester film to a first heat treatment at 70°C and a preheat treatment at 160°C, and then cutting it into 1 cm × 1 cm pieces, is mixed with a polyethylene terephthalate (PET) sample obtained by passing a polyethylene terephthalate (PET) container through a 12.5 mm mesh sieve in a weight ratio of 3:

97. This mixed sample is then heat-treated at 195°C for 90 minutes, and the heat-treated mixed sample is passed through the sieve to evaluate the crystallinity of the polyester oriented film, as shown in Equation 2 below: [Formula 2] Crystallization fraction (%) = (F Ｔ / F ｍ )×100 [In equation 2, F Ｔ The weight (S) of the heat-treated mixed sample that passed through a 12.5 mm mesh sieve is the weight of the sample. ｓ The total weight (M) of the heat-treated mixed sample Ｔ The ratio to (S ｓ / M Ｔ ) × 100, %) and F ｍ This is the weight (C) of the aggregated sample remaining on the 12.5 mm mesh sieve from the heat-treated mixed sample. ｓ The total weight (M) of the heat-treated mixed sample Ｔ ) Ratio to ((C ｓ / M Ｔ ) × 100, %) An oriented polyester film having a crystal fraction of 30% or more, as expressed by [formula].

8. The following formula 1-1: [Math 1] [In Equation 1-1, L ２５ L is the initial length in the transverse direction (TD) of the oriented polyester film sample at 25°C. ８０ This is the length of the transverse direction (TD) of the oriented polyester film sample after immersion in 80°C water for 10 seconds. An oriented polyester film according to claim 1 or 7, having a heat shrinkage rate of 40% or more when represented by [the specified formula].

9. The glycol components are bis(2-hydroxyethyl) terephthalate, isosorbide, neopentyl glycol, ethylene glycol, cyclohexanedimethanol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, and 3-methyl-2,4-pentanediol. An oriented polyester film according to claim 1 or 7, comprising at least one selected from the group consisting of 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, 4-(hydroxymethyl)cyclohexylmethyl-4-(hydroxymethyl)cyclohexanecarboxylate, 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol, regenerated cyclohexanedimethanol, regenerated ethylene glycol, regenerated bis(2-hydroxyethyl)terephthalate, and regenerated diethylene glycol.

10. The oriented polyester film according to claim 1 or 7, wherein the dicarboxylic acid component comprises at least one selected from the group consisting of isophthalic acid, terephthalic acid, dimethyl isophthalate, phthalic acid, dimethyl phthalate, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, dimethyl 2,6-naphthalenedicarboxylate, diphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, dimethyl 1,4-cyclohexanedicarboxylate, dimethyl 1,3-cyclohexanedicarboxylate, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, glutaric acid, azelaic acid, regenerated isophthalic acid, regenerated terephthalic acid, regenerated dimethyl isophthalate, and regenerated dimethyl phthalate.

11. An oriented polyester film according to claim 1 or 7, wherein the polyester resin has an intrinsic viscosity (IV) of 0.5 dl / g to 1.2 dl / g.

12. A step of polymerizing a diol component and a dicarboxylic acid component to prepare a polyester resin, The steps include preparing an oriented polyester sheet from the aforementioned polyester resin, The steps of heat-fixing the orientation sheet and Includes, When the film is subjected to a first heat treatment and a second heat treatment, and then analyzed by differential scanning calorimetry (DSC), the first melting point (Tm １ ) and the second melting point (Tm ２ ) appeared, Second melting point (Tm ２ The second heat of fusion (H) in ) ２ The first melting point (Tm) of ) １ The first heat of fusion (H) in ) １ ) Ratio (H ２ / H １ A method for preparing an oriented polyester film in which the ratio of ) is 0.1 or higher.

13. A method for preparing an oriented polyester film according to claim 12, wherein the first heat treatment is carried out at 60 to 105°C for 1 minute or less.

14. A method for preparing an oriented polyester film according to claim 12, wherein the second heat treatment is carried out at 140 to 220°C for 4 hours or less.

15. A method for preparing an oriented polyester film according to claim 12, wherein the second heat treatment is performed after preheating the oriented polyester film subjected to the first heat treatment at 140 to 220°C for 1 to 30 minutes.

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