Polyester heat-shrinkable film and method for producing polyester resin film

Abstract

Provided is a polyester heat-shrinkable film or the like that stably shrinks even when applied to various PET bottles and the like, and exhibits excellent wrinkle resistance. It is a polyester heat-shrinkable film or the like having the following configurations (a) to (d). (a) The thermal shrinkage ratio A1 in the main shrinkage direction when shrunk in warm water at 80°C for 10 seconds is set to a value within the range of 21 to 65%. (b) The thermal shrinkage ratio A2 in the direction orthogonal to the main shrinkage direction when shrunk in warm water at 80°C for 10 seconds is set to a value within the range of -5 to 10%. (c) The absolute value of the ratio of the thermal shrinkage ratios A1 and A2 (A1 / A2) is set to a value of 5.5 or greater. (d) The necking ratio measured in warm water at 70°C for 10 seconds is set to a value of 6% or less.

Description

Technical Field

[0001] This invention relates to a polyester-based heat-shrinkable film (hereinafter, sometimes simply referred to as heat-shrinkable film) and a method for manufacturing a polyester-based resin film. Specifically, this relates to a polyester heat-shrinkable film that exhibits excellent wrinkle resistance even when applied to PET bottles of various shapes through control including the necking rate, and a method for manufacturing the same. Background Technology

[0002] Previously, heat shrink film was widely used as a substrate film for labeling PET bottles and other products. In particular, polyester-based heat shrink film is seeing its share of the market as a substrate film for labeling grow due to its superior strength and transparency. While polyester heat shrink film possesses the aforementioned excellent properties, it exhibits uneven shrinkage during heating due to its rapid thermal response, making it prone to wrinkling. Specifically, the heat shrinkage rate at a specified temperature can deviate from the film's performance under varying storage conditions, particularly humidity, leading to wrinkles during the heat shrinking process of the shrink label.

[0003] In response, a polyester shrink film with excellent water resistance, shrinkage properties and strength has been proposed. It is a heat-shrinkable polyester film that can be applied to heat-resistant PET bottles with narrow necks and cylindrical shapes (for example, see Patent Document 1). More specifically, the heat-shrinkable polyester film satisfies the following important conditions (1) to (3), and is preferred when it satisfies important condition (4). (1) The thermal shrinkage rate of the film in the main shrinkage direction after 5 minutes in an air oven at 100°C is more than 20% in either the longitudinal or transverse direction. (2) The breaking elongation of the membrane in the direction orthogonal to the contraction direction is a value in the range of 1 to 100%. (3) The heat of fusion of the membrane is less than 8 cal / g. (4) The neck shrinkage rate after immersion in warm water at 75°C for 5 seconds is less than 10%.

[0004] In addition, a heat-shrinkable polyester film that suppresses wrinkling when used in applications such as strip label packaging for lunch boxes or noodle containers is proposed (see, for example, Patent Document 2). More specifically, it is a heat-shrinkable polyester film with the longitudinal (long side) direction as the main shrinkage direction, which satisfies the following important conditions (1) to (6). (1) The thermal shrinkage rate in the long side direction after immersion in warm water at 80°C for 10 seconds is more than 35% and less than 70%. (2) The thermal shrinkage rate in the direction orthogonal to the long side (width direction) after immersion in warm water at 80℃ for 10 seconds is more than -8% and less than 7%. (3) The change rate of the membrane width direction is within the range of 5 to 22% when the long side is set to a constant length and only the long side is fixed, and the membrane is held in hot air at 90°C for 10 seconds. (4) The change rate of the membrane width direction was measured in the range of 5 to 20% by setting the long side direction to a relaxed state of 10% and fixing only the long side direction, and holding it in hot air at 90°C for 10 seconds. (5) The maximum thermal shrinkage stress in the long side direction measured under hot air at 90℃ is a value in the range of 2~10MPa. (6) The stress (i.e., the so-called F10) measured under hot air at a temperature of 90°C when stretched by 10% is in the range of 1 to 5 MPa in the long side direction and in the range of 0.5 to 3 MPa in the width direction.

[0005] In addition, a heat-shrinkable film with excellent durability and coverage retention when applied to battery cell packaging and the like has been proposed (for example, see Patent Document 3). More specifically, it is a single-layer or multi-layered heat-shrinkable film having a resin layer comprising a polyester resin as the main component on at least one side of the film, which satisfies the following important conditions (a) to (d), and is preferred when it satisfies important condition (e). (a) The polyester resin includes a copolyester resin and, in addition to the specified copolymer components, includes at least one of the group consisting of 1,4-butanediol, neopentyl glycol, diethylene glycol, etc., and includes a diol component other than ethylene glycol that is 15 mol% or more of the diol component relative to 100 mol% of the total amount. (b) The thermal shrinkage rate in the main shrinkage direction after immersion in warm water at 99°C for 10 seconds is a value in the range of 40% to 65%. (c) The thermal shrinkage rate in the direction orthogonal to the main shrinkage direction after immersion in warm water at 99°C for 10 seconds is a value in the range of 4 to 15%. (d) The difference between the thermal shrinkage rate in the main shrinkage direction and the thermal shrinkage rate in the direction orthogonal to the main shrinkage direction after immersion in warm water at 99°C for 10 seconds (thermal shrinkage rate in the main shrinkage direction - thermal shrinkage rate in the direction orthogonal to the main shrinkage direction) is a value in the range of 30% to 55%. (e) The neck shrinkage rate after immersion in warm water at 70°C for 10 seconds is less than 5%. Existing technical documents Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 07-77757 (claims, etc.) Patent Document 2: WO2020-246420 (claims, etc.) Patent Document 3: Japanese Patent No. 6791335 (claims, etc.) Summary of the Invention (a) Technical problems to be solved

[0007] However, in the case of heat-shrinkable polyester films disclosed in Patent Document 1, important conditions (1) to (3) need to be fully met. Not only is the management of manufacturing conditions strict, but there is also the problem that the output during manufacturing is easy to be reduced. In addition, as an important condition (4), the neck shrinkage rate after immersion in warm water at 75°C for 5 seconds is preferably less than 10%, but this is only considered for applications such as narrow-necked heat-resistant PET bottles, which are the conventional form. Therefore, when applied to PET bottles or other containers with complex shapes rather than circular horizontal cross-sections, uneven heat shrinkage can easily occur, leading to fine wrinkles.

[0008] Furthermore, in the case of the heat-shrinkable polyester film disclosed in Patent Document 2, the manufacturing process requires uniaxial stretching of an unstretched sheet of polyester with a specific composition along the long side, followed by relaxation treatment along the long side. This not only requires strict management of manufacturing conditions but also presents the problem of easily reducing production output during manufacturing. Furthermore, it must fully satisfy important conditions (1) to (6), especially important condition (3), for the rate of change of the membrane width direction calculated by the specified formula under the condition that the long side direction is set to a constant length and only the long side direction is fixed, and the membrane is held in hot air at 90°C for 10 seconds, it must be limited to a specified value (5 to 22%). Furthermore, as an important condition (4), the rate of change in the membrane width direction calculated by the prescribed formula needs to be limited to a prescribed value (5~20%) when the long side direction is set to a relaxed state of 10% and only the long side direction is fixed, and the membrane is held for 10 seconds under hot air at 90°C. This is difficult to control stably. That is, especially when measuring and controlling important conditions (3) and important conditions (4), it is necessary to set the specified membrane to a fixed state in the long side direction and use a heating condition of 90°C hot air for 10 seconds, or to reproduce the specified relaxation state. There is a problem that the values ​​of the change rate obtained separately are prone to large deviations. Furthermore, when the label is primarily used for food containers or noodle containers, and is applied to PET bottles with complex shapes, there is a problem that the heat shrinkage can become uneven, easily resulting in fine wrinkles.

[0009] Furthermore, in the case of heat-shrinkable polyester films disclosed in Patent Document 3, it is necessary to fully meet the important conditions (a) to (d). Not only are there many management items for manufacturing conditions, including the selection of raw materials, but there is also the problem that it is difficult to control stably and the output during manufacturing is easy to decrease. In addition, as an important condition (e), the neck shrinkage rate after immersion in warm water at 70°C for 10 seconds is preferably less than 5%. However, it is mainly used for applications such as packaging for battery cells used in vehicles. When applied to PET bottles with complex shapes, the heat shrinkage is prone to become uneven and fine wrinkles are easily generated.

[0010] In view of the above-mentioned technical problems, the inventors of the present invention have conducted in-depth research and solved the existing technical problems by limiting the absolute value of the ratio of the heat shrinkage rate of the heat shrinkage film in the main shrinkage direction and the direction orthogonal to the main shrinkage direction, which are measured under specified conditions, and limiting the necking rate measured under specified conditions. In other words, the object of the present invention is to provide a polyester heat-shrinkable film that not only has fewer management items and is easy to manufacture stably, but also exhibits excellent wrinkle resistance when heat-shrinkable even when applied to PET bottles with complex shapes, and a stable manufacturing method for the polyester resin film. (II) Technical Solution

[0011] According to the present invention, a polyester heat shrink film derived from a polyester resin is provided, characterized by having the following configurations (a) to (d), which can solve the above-mentioned problems. (a) When the thermal shrinkage rate in the main shrinkage direction is defined as A1 when shrinkage is performed in warm water at 80°C for 10 seconds, A1 is set to a value in the range of 21% to 65%. (b) When the thermal shrinkage rate in the direction orthogonal to the main shrinkage direction is defined as A2 when shrinking in warm water at 80°C for 10 seconds, A2 is set to a value in the range of -5 to 10%. (c) Set the absolute value of the ratio of heat shrinkage rates A1 to A2 (A1 / A2) to a value of 5.5 or higher. (d) The necking rate measured under the conditions of 70°C in warm water for 10 seconds is set to a value of 6% or less. That is, by limiting the heat shrinkage rate in the main shrinkage direction (a) and the heat shrinkage rate in the direction orthogonal to the main shrinkage direction (b) under specified conditions, the absolute value of the ratio of the heat shrinkage rate in the main shrinkage direction and the heat shrinkage rate in the direction orthogonal to the main shrinkage direction of the heat shrink film measured under specified conditions (c), and limiting the necking rate measured under specified conditions (d), it is not only easy to manufacture stably, but also can exhibit excellent wrinkle resistance when applied to various PET bottles, etc.

[0012] Furthermore, in the polyester heat shrink film according to the present invention, when the maximum shrinkage stress in the main shrinkage direction at a shrinkage temperature of 85°C is set as C, the value of C is preferably set to a value in the range of 3 to 10 MPa. By limiting the maximum shrinkage stress (C) at a specified temperature to a specified range as described above, the control of necking rate and other factors becomes easier, and excellent wrinkle resistance can be achieved more stably.

[0013] Furthermore, the polyester heat-shrinkable film according to the present invention preferably has a thickness in the range of 10 to 100 μm. By limiting the thickness to a specified range as described above, it becomes easier to control the heat shrinkage rate, necking rate, etc. under specified conditions, thereby enabling the excellent wrinkle resistance to be performed more stably.

[0014] Furthermore, in the polyester heat shrink film according to the present invention, the main shrinkage direction of the polyester heat shrink film is preferably the MD direction. By limiting the main shrinkage direction to the MD direction as described above, in particular, it becomes easier to adjust the manufacturing conditions of the longitudinal shrinkage film, and it also becomes easier to control the heat shrinkage rate (A1 and A2), necking rate, absolute value (A1 / A2), shrinkage stress, etc. under specified conditions, thereby further enhancing the excellent wrinkle resistance.

[0015] Furthermore, in the polyester heat-shrinkable film according to the present invention, the polyester resin is preferably a polyester resin derived from dicarboxylic acid compounds and diol compounds as reactants, and the diol compounds include at least ethylene glycol, diethylene glycol and 1,4-cyclohexanediethanol. By specifically limiting the types of diol compounds that are one of the reactants as described above, it becomes easier to adjust the heat shrinkage rate (A1 and A2), necking rate, absolute value (A1 / A2), shrinkage stress, etc. under specified conditions, thereby further enhancing the excellent wrinkle resistance.

[0016] In addition, another aspect of the present invention is a method for manufacturing a polyester resin film derived from dicarboxylic acid compounds and diol compounds as reactants, characterized by comprising the following steps 1 to 2. Step 1: The process of preparing dicarboxylic acid compounds and diol compounds as reactants and reacting them to prepare polyester resins. Step 2: A step of manufacturing a polyester heat shrink film having the following configurations (a) to (d) by stretching polyester resin along the TD direction and the MD direction, or either of these directions. (a) When the thermal shrinkage rate in the main shrinkage direction is defined as A1 when shrinkage is performed in warm water at 80°C for 10 seconds, A1 is set to a value in the range of 21% to 65%. (b) When the thermal shrinkage rate in the direction orthogonal to the main shrinkage direction is defined as A2 when shrinking in warm water at 80°C for 10 seconds, A2 is set to a value in the range of -5 to 10%. (c) Set the absolute value of the ratio of heat shrinkage rates A1 to A2 (A1 / A2) to a value of 5.5 or higher. (d) The necking rate measured under the conditions of 70°C in warm water for 10 seconds is set to a value of 6% or less. That is, by manufacturing polyester heat shrink film in the manner described above, it is possible to effectively manufacture polyester heat shrink film that exhibits excellent wrinkle resistance even when the main shrinkage direction is the so-called transverse (TD direction) or longitudinal (MD direction) and is applied to various PET bottles, etc.

[0017] Furthermore, in the method for manufacturing the polyester heat-shrinkable film of the present invention, it is preferable to perform the stretching process in step 2 along the MD direction. By setting the stretching direction to the MD direction as described above, it becomes easier to adjust the manufacturing conditions of the longitudinal shrinkage film, and it also becomes easier to control the heat shrinkage rate (A1 and A2), necking rate, absolute value (A1 / A2), shrinkage stress, etc. under specified conditions, thereby further enhancing the excellent wrinkle resistance. Attached Figure Description

[0018] Figure 1 Figures (a) to (c) in the figure illustrate the morphology of polyester heat shrink film. Figure 2 Figure (a) is a graph illustrating the relationship between the heat shrinkage rate (A1) in the main shrinkage direction of a polyester heat shrink film and the evaluation (relative value) of shrinkage unevenness under specified heating conditions (80°C warm water, 10 seconds). Figure 2 (b) is a graph illustrating the relationship between the heat shrinkage rate (A2) of a polyester heat shrink film in a direction orthogonal to the main shrinkage direction and the evaluation (relative value) of shrinkage unevenness under specified heating conditions (80°C warm water, 10 seconds). Figure 3This is a graph illustrating the relationship between the absolute value (A1 / A2) of the ratio of the heat shrinkage rate (A1) in the main shrinkage direction of the polyester heat shrink film to the heat shrinkage rate (A2) in the direction orthogonal to the main shrinkage direction, and the evaluation of uneven shrinkage (relative value). Figure 4 This is a graph illustrating the relationship between necking rate (%) and the evaluation of uneven shrinkage (relative value) of polyester heat shrink film under specified heating conditions (warm water 70°C, 10 seconds). Figure 5 This is a graph illustrating the relationship between the shrinkage stress (MPa) in the main shrinkage direction and the evaluation (relative value) of uneven shrinkage under specified heating conditions (85°C, 10 seconds) for polyester heat shrink film. Figure 6 (a) is a diagram (photograph) showing the appearance of the cylindrical label in the absence of uneven shrinkage, corresponding to Example 1. Figure 6 (b) to (d) in the text refer to... Figure 6 The diagram (a) shows an enlarged view of the regions P, Q, and R. Figure 7 (a) is a diagram (photograph) showing the appearance of the cylindrical label in the case of uneven shrinkage, corresponding to Comparative Example 1. Figure 7 (b) to (d) in the text refer to... Figure 7 The diagram (a) shows an enlarged view of the regions S, T, and U. Figure 8 (a) in the figure is a diagram provided to illustrate the test sample for determining the necking rate. Figure 8 Figure (b) is provided to illustrate the fixed frame fixture used for measuring necking rate. Figure 8 (c) in the figure is provided to illustrate the method for determining necking rate. Detailed Implementation

[0019] [First Implementation Plan] like Figure 1 As shown in (a) to (c), the first embodiment is a polyester heat shrink film, which is a polyester heat shrink film derived from polyester resin, characterized in that it has the following configuration (a) to (d). (a) When the thermal shrinkage rate in the main shrinkage direction is defined as A1 when shrinkage is performed in warm water at 80°C for 10 seconds, A1 is set to a value in the range of 21% to 65%. (b) When heat shrinkage is performed in warm water at 80°C for 10 seconds, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction (hereinafter, sometimes simply referred to as the orthogonal direction) is set as A2, and A2 is set to a value in the range of -5 to 10%. (c) Set the absolute value of the ratio of heat shrinkage rates A1 to A2 (A1 / A2) to a value of 5.5 or higher. (d) The necking rate measured under the conditions of 70°C in warm water for 10 seconds is set to a value of 6% or less. The following will be divided according to the composition of the polyester heat shrink film of the first embodiment, and various parameters will be explained with reference to the accompanying drawings as appropriate, and the scheme of the polyester heat shrink film will be specifically described.

[0020] 1. Polyester resin The polyester resin used as the main component is not limited in type as long as it is a polyester resin that can easily satisfy the above-described (a) to (d) structures. Generally, the preferred types are: polyester resins composed of diols and dicarboxylic acids; polyester resins composed of diols and hydroxycarboxylic acids; polyester resins composed of diols, dicarboxylic acids and hydroxycarboxylic acids; or mixtures of these polyester resins. Among them, diols used as raw material components of polyester resins can include at least one of the following: ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol, hexanediol and other aliphatic diols, 1,4-cyclohexanediethanol and other alicyclic diols, aromatic diols, etc. Furthermore, among the aforementioned diols, ethylene glycol, diethylene glycol, and 1,4-cyclohexanediethanol are particularly preferred. In addition, dicarboxylic acids that are also components of polyester resins can be listed as at least one of the following: fatty acid dicarboxylic acids such as adipic acid, sebacic acid, and azelaic acid; aromatic dicarboxylic acids such as terephthalic acid, naphthalic acid, and isophthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; or ester-forming derivatives of these dicarboxylic acids. Furthermore, among the aforementioned dicarboxylic acids, terephthalic acid and isophthalic acid are particularly preferred. In addition, hydroxycarboxylic acids, which are also components of polyester resins, can be listed as at least one of the following: lactic acid, hydroxybutyric acid, polycaprolactone, etc.

[0021] Furthermore, as an amorphous polyester resin, for example, an amorphous polyester resin composed of a dicarboxylic acid and a diol is preferred, wherein the dicarboxylic acid comprises at least 80 mol% terephthalic acid, and the diol is composed of 50-80 mol% ethylene glycol and 20-50 mol% one or more diols selected from 1,4-cyclohexanediol, neopentyl glycol, and diethylene glycol. Other dicarboxylic acids and diols, or hydroxycarboxylic acids, may also be used to modify and adjust the properties of the film as needed. Furthermore, they can be used individually or as a mixture. On the other hand, as crystalline polyester resins, there are polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and polypropylene terephthalate, which are preferred for use whether individually or in mixtures.

[0022] Furthermore, when the polyester resin is a mixture of crystalline polyester resin and amorphous polyester resin, in order to obtain good and appropriate wrinkle resistance, heat resistance and heat shrinkage rate, the amount of crystalline polyester resin is preferably set to a value in the range of 10 to 50% by weight relative to the total amount (100% by weight) of the resin constituting the polyester heat shrink film. The reason is that by setting the amount of crystalline polyester resin to a value within a specified range as described above, it is possible to produce a polyester heat-shrinkable film that exhibits good heat-shrinkage properties while also showing little change in physical properties such as heat shrinkage rate at a specified temperature, even under high humidity conditions. More specifically, if the content of crystalline polyester resin is less than 10% by weight, it is difficult to suppress moisture absorption when placed in a specified high humidity environment for a short period of time, and sometimes it is difficult to control the absolute value (A1 / A2) of the specified heat shrinkage ratio within the specified range. However, if the content of crystalline polyester resin is greater than 50%, the shrinkage rate of the obtained polyester heat shrink film may sometimes decrease excessively. Therefore, relative to the total amount of resin (100% by weight), it is more preferable to set the amount of crystalline polyester resin in the range of 15 to 45% by weight, and even more preferably in the range of 20 to 40% by weight.

[0023] 2. Composition (a) For polyester heat shrinkable film, configuration (a) is a necessary condition for setting the heat shrinkage rate A1 (%) in the main shrinkage direction when shrinking in warm water at 80°C for 10 seconds to a value in the range of 21 to 65%. The reason is that if the heat shrinkage rate A1 exceeds this range, the heat shrinkage rate under commonly used heat shrinkage conditions (80°C, 10 seconds) will sometimes become insufficient. For PET bottles, it will become unable to follow the shape of the bottle body and it will be difficult to suppress the formation of wrinkles. More specifically, if the thermal shrinkage rate A1 of the film becomes less than 21%, it may become difficult to limit the value represented by the absolute value (A1 / A2) to the specified range. The balance between the thermal shrinkage rate in the main shrinkage direction and the direction orthogonal to it decreases, making it difficult to suppress the formation of wrinkles. However, if the thermal shrinkage rate A1 of the film becomes too large, it will sometimes become difficult to limit the value represented by the absolute value (A1 / A2) within the specified range. The balance between the thermal shrinkage rate of the main shrinkage direction and the direction orthogonal to it will decrease, making it difficult to suppress the formation of wrinkles. Therefore, it is more preferable to set the thermal shrinkage rate A1 of the film to a value in the range of 25 to 50%, and even more preferably to set it to a value in the range of 30 to 45%. Furthermore, when measuring the aforementioned heat shrinkage rate A1, it is more preferable to measure the heat shrinkage rate A1 for the main shrinkage direction before and after placing the film under high humidity conditions of 20°C and 90%RH for 24 hours, preferably under specified conditions. Therefore, although not specifically stated, when measuring the heat shrinkage rate A1, it is assumed that the film has been placed under specified conditions and stabilized.

[0024] Here, it is mentioned Figure 2 (a) illustrates the relationship between the heat shrinkage rate A1 (%) and wrinkle resistance (relative value) measured under specified conditions. That is, in Figure 2 In (a), the heat shrinkage rate of the main shrinkage direction measured under the heat shrinkage conditions of immersion in warm water at 80°C for 10 seconds is shown as A1 (%) on the horizontal axis, and the wrinkle resistance evaluation (relative value) is shown on the vertical axis. In addition, the evaluation of wrinkle resistance on the vertical axis (relative value) is a numerical value, in which evaluation ◎ is set to 5 points, evaluation ○ is set to 3 points, evaluation △ is set to 1 point, and evaluation × is set to 0 points. also, Figure 2 The characteristic curve data in (a) are based on Examples 1, 3-7 described later (in Figure 2 In (a) of the document, it is marked as Ex1, 3-7, wherein Example 2 is omitted from the perspective of manufacturing conditions. ) and Comparative Examples 1-3 (in Figure 2 (a) shows the evaluation results of the relationship between the heat shrinkage rate and wrinkle resistance of polyester heat shrink films in the main shrinkage direction.

[0025] according to Figure 2 The characteristic curve in (a) can be considered to show that the relationship between the thermal shrinkage rate A1 in the main shrinkage direction measured under specified conditions and the wrinkle resistance has certain characteristics. More specifically, according to Figure 2 As can be seen from the characteristic curve in (a), for example, by limiting the heat shrinkage rate A1 to below 55%, a good result of at least 4 was obtained in the evaluation of wrinkle resistance. Similarly, by limiting the heat shrinkage rate A1 to below 50%, a better result was obtained (5). However, it was also determined that if the value of the heat shrinkage rate A1 becomes too small, the adhesion to the adhered objects such as PET bottles will decrease significantly. Therefore, regarding composition (a), by setting the heat shrinkage rate A1 (%) in the main shrinkage direction when shrinking in warm water at 80°C for 10 seconds to a value in the range of 21 to 55%, good wrinkle resistance can be obtained while maintaining excellent adhesion to the adhered material such as PET bottles.

[0026] 3. Composition (b) For polyester heat shrink film, configuration (b) is a necessary condition for setting the heat shrinkage rate A2 in the direction orthogonal to the main shrinkage direction when heat shrinking in warm water at 80°C for 10 seconds to a value in the range of -5 to 10%. The reason is that if the heat shrinkage rate A2 exceeds the specified range, the heat shrinkage rate under the commonly used heat shrinkage conditions (80°C, 10 seconds) may become insufficient, or even excessive. For PET bottles, this makes it impossible to follow the shape of the bottle body and prevents wrinkles from forming.

[0027] Furthermore, if the thermal shrinkage rate A2 of the film becomes less than -5%, it may become difficult to limit the value represented by the absolute value (A1 / A2) to the specified range, which in turn reduces the balance between the thermal shrinkage rate of the main shrinkage direction and the direction orthogonal to it, making it difficult to suppress the formation of wrinkles. However, if the thermal shrinkage rate A2 of the film becomes too large and exceeds 10%, it will sometimes become difficult to limit the value represented by the absolute value (A1 / A2) within the specified range, which will reduce the balance between the thermal shrinkage rate of the main shrinkage direction and the direction orthogonal to it, making it difficult to suppress the formation of wrinkles. Therefore, it is preferable to set the thermal shrinkage rate A2 of the film in the orthogonal direction to a value in the range of -4 to 8%, and more preferably to a value in the range of -3 to 5%.

[0028] Furthermore, in addition to stabilizing the film by placing it under high humidity conditions of 20°C and 90%RH for 24 hours before measuring the heat shrinkage rate A1 as described above, it is preferable to stabilize the film by placing it under high humidity conditions of 20°C and 90%RH for 24 hours before measuring the heat shrinkage rate A2.

[0029] Here, it is mentioned Figure 2 (b) illustrates the relationship between the heat shrinkage rate A2 (%) measured under specified conditions and the wrinkle resistance (the relative value of the evaluation). That is, in Figure 2In (b), the heat shrinkage rate in the direction orthogonal to the main shrinkage direction, measured under the heat shrinkage condition of immersion in warm water at 80°C for 10 seconds, is shown as A2 (%) on the horizontal axis, and the wrinkle resistance evaluation (relative value) is shown on the vertical axis. The evaluation of wrinkle resistance on the vertical axis (relative value) is a numerical value, where evaluation ◎ is set to 5 points, evaluation ○ to 3 points, evaluation △ to 1 point, and evaluation × to 0 points. also, Figure 2 The characteristic curves in (b) are based on Examples 1, 3-7 described later (in Figure 2 In (b) of the document, marked Ex1, 3-7, Example 2 is omitted from the perspective of manufacturing conditions. Comparative Examples 1-3 (in...) Figure 2 (b) CE1~3 shows the evaluation results of the relationship between the heat shrinkage rate and wrinkle resistance of polyester heat shrink films in a direction orthogonal to the main shrinkage direction. According to this Figure 2 The characteristic curve in (b) suggests that there is a certain relationship between the thermal shrinkage rate A2 (%) measured under specified conditions in the direction orthogonal to the main shrinkage direction and the wrinkle resistance. More specifically, for example, by limiting the heat shrinkage rate A2 to the range of -5 to 10%, a good result of at least 3 was obtained in the evaluation of wrinkle resistance. Similarly, by limiting the heat shrinkage rate A2 to the range of -5 to 5%, all results above 5 were obtained. In any case, regarding composition (b), good wrinkle resistance can be obtained by setting the heat shrinkage rate A2 (%) in the direction orthogonal to the main shrinkage direction when heat-shrinking in warm water at 80°C for 10 seconds to a value within a specified range.

[0030] 4. Composition (c) Configuration (c) is a necessary condition that aims to set the absolute value (A1 / A2) of the ratio of the thermal shrinkage rate A1 in the main shrinkage direction to the thermal shrinkage rate A2 in the direction orthogonal to it, as measured under specified conditions, to be 5.5 or more. The reason is that by controlling the value represented by the absolute value (A1 / A2) as described above, it can complement other components (a)~(b) and (d) to obtain a good evaluation of anti-wrinkle properties. Conversely, by setting the absolute value (A1 / A2) to a value of 5.5 or higher, the changes in heat shrinkage rate at the specified temperature are small, and heat shrinkage can be performed stably and with good reproducibility under the specified conditions, making it easier to achieve excellent wrinkle resistance. However, if this absolute value (A1 / A2) becomes too large, it may sometimes reduce the balance between the thermal shrinkage rate A1 in the main shrinkage direction and the thermal shrinkage rate A2 in the orthogonal direction, resulting in a decrease in wrinkle resistance. Therefore, as a configuration (c), it is more preferable to set the absolute value (A1 / A2) to a value in the range of 10 to 150, and even more preferable to set it to a value in the range of 15 to 100.

[0031] Here, it is mentioned Figure 3 This explains the relationship between the absolute value (A1 / A2) of the ratio of the heat shrinkage rate (A1) in the main shrinkage direction to the heat shrinkage rate (A2) in the direction orthogonal to the main shrinkage direction under specified heat shrinkage conditions (immersion in warm water at 80°C for 10 seconds) of polyester heat shrink film and uneven shrinkage. That is, the absolute value (A1 / A2) of the ratio of the heat shrinkage rate is shown on the horizontal axis, and the evaluation value (relative value) of the uneven shrinkage is shown on the vertical axis. In addition, according to Figure 3 The characteristic curves in the figure show that there is an excellent correlation between the absolute value of the ratio of thermal shrinkage (A1 / A2) and the uneven shrinkage. Therefore, by limiting the absolute value of the ratio of heat shrinkage rates (A1 / A2) to a specified range, uneven shrinkage can be controlled with good precision.

[0032] 5. Composition (d) For polyester heat shrinkable films, configuration (d) is a necessary configuration condition aimed at setting the necking rate to a value of 6% or less. That is, generally, taking into account the necking phenomenon that occurs during film production, by limiting the necking rate that simulates this phenomenon to a specified range, excellent wrinkle resistance can be achieved even when applied to various PET bottles, etc. However, if the necking ratio becomes too small, it can sometimes limit production output and the types of raw materials that can be used, which is economically disadvantageous. Therefore, it is more preferable to set the necking rate to a value in the range of 0 to 5%, and even more preferable to set it to a value in the range of 0.1 to 3%. Furthermore, the method for measuring the necking rate will be described in detail in Example 1 and the like later.

[0033] Here, it is mentioned Figure 4 This is to illustrate the relationship between neck shrinkage rate (%) and wrinkle resistance (a relative value of the evaluation) measured under specified conditions. That is, in Figure 4 The neck shrinkage rate (%) measured under heat shrinkage conditions of immersion in warm water at 70°C for 10 seconds is shown on the horizontal axis, and the wrinkle resistance evaluation (relative value) is shown on the vertical axis. The evaluation of wrinkle resistance on the vertical axis (relative value) is a numerical value, where evaluation ◎ is set to 5 points, evaluation ○ to 3 points, evaluation △ to 1 point, and evaluation × to 0 points. also, Figure 4 The characteristic curves are based on Examples 1, 3-7 described later (in... Figure 4 Examples 1, 3-7 are labeled Ex1, 3-7, where Example 2 is omitted from the perspective of manufacturing conditions. Comparative Examples 1-3 (in...) Figure 4 It was made based on the evaluation results of the wrinkle resistance of polyester heat shrink film (marked as CE1~3). According to this Figure 4 The characteristic curves in the data suggest that there is a certain relationship between neck shrinkage rate (%) and wrinkle resistance (relative value). More specifically, according to Figure 4 As can be seen from the characteristic curves, for example, by limiting the neck shrinkage rate to below 6%, a good relative value of at least 3 was obtained in the evaluation of wrinkle resistance. Similarly, by limiting the neck shrinkage rate to below 5%, a better result of 5 was obtained in the evaluation of wrinkle resistance. In any case, regarding composition (d), good wrinkle resistance can be obtained by setting the necking rate when heat-shrinked under specified conditions to a value of 6% or less.

[0034] 6. Arbitrary constitutive conditions (1) Composition (e) For the polyester heat-shrinkable film of the first embodiment, configuration (e) is a configuration condition related to the thickness (average thickness) of the film before heat shrinking, which is an arbitrary configuration condition that aims to: generally set the thickness of the film before heat shrinking to a value in the range of 10 to 100 μm. That is, by specifically limiting the thickness of the film before heat shrinkage to a value within a specified range as described above, it becomes easier to control the heat shrinkage rate (A1 and A2), necking rate, absolute value (A1 / A2), shrinkage stress, etc. under specified conditions. Therefore, it can reduce the influence of specified factors, suppress uneven shrinkage in polyester heat-shrinkable films caused by rapid thermal response during heat shrinkage, and also suppress the formation of fine wrinkles. More specifically, if the thickness of the film before heat shrinkage is less than 10 μm or greater than 100 μm, it may sometimes become unable to suppress the uneven shrinkage caused by the rapid thermal response in the polyester heat shrink film during heat shrinkage, and may be unable to suppress the formation of fine wrinkles. Therefore, as a configuration (e), it is more preferable to set the thickness of the film before heat shrinkage to a value in the range of 30 to 80 μm, and even more preferably to set it to a value in the range of 40 to 60 μm.

[0035] (2) Composition (f) For the polyester heat-shrinkable film of the first embodiment, configuration (f) is a configuration condition in which the maximum shrinkage stress in the TD direction at a shrinkage temperature of 85°C is set as C, and C is set as any value in the range of 3 to 10 MPa. That is, such as Figure 5 As shown, by controlling the maximum shrinkage stress within a specified range, effective wrinkle resistance can be achieved, and wrinkles caused by excessive or insufficient maximum shrinkage stress during heat shrinkage can be effectively suppressed. also, Figure 5 The characteristic curves are based on Examples 1, 3-7 described later (in... Figure 5 The films were prepared based on the evaluation results of the wrinkle resistance of polyester heat-shrinkable films, which are designated as Ex1, 3 to 7 (Examination 2 is omitted from the perspective of manufacturing conditions). Comparative Examples 1 to 3 (designated as CE1 to CE3) were also included. More specifically, such as Figure 5 As shown, if the maximum shrinkage stress C becomes greater than 10 MPa, the maximum shrinkage stress during heat shrinkage becomes excessive. When it is installed on plastic bottles, the shape of the plastic bottle may sometimes be deformed, or wrinkles may be produced due to the deformation, resulting in a decrease in wrinkle resistance. On the other hand, such as Figure 5 As shown, if the value of the maximum shrinkage stress C becomes too small, for example, less than 4 MPa, the maximum shrinkage stress during heat shrinkage may be insufficient, which may create gaps between the plastic bottle and the film, thereby reducing the wrinkle resistance. Therefore, as a configuration (f), it is more preferable to set the maximum shrinkage stress C to a value in the range of 4.1 to 8 MPa, and even more preferably to set it to a value in the range of 5 to 7 MPa.

[0036] (3) Other 1 It is preferable to incorporate various additives into the polyester heat shrink film of the first embodiment, or to attach various additives to one or both sides of the polyester heat shrink film of the first embodiment. More specifically, generally, relative to the total amount of polyester heat shrink film, at least one of the following is preferably incorporated in the range of 0.01 to 10% by weight, more preferably in the range of 0.1 to 1% by weight: anti-hydrolysis agent, antistatic agent, ultraviolet absorber, infrared absorber, colorant, organic filler, inorganic filler, organic fiber, inorganic fiber, etc.

[0037] In addition, such as Figure 1 As shown in (b), it is also preferable to laminate other resin layers 10a, 10b containing at least one of the various additives described above onto one or both sides of the polyester heat shrink film 10. In this case, it is preferable that when the thickness of the polyester heat shrink film is set to 100%, the single-layer thickness or total thickness of the additional resin layers is typically set to a value in the range of 0.1% to 10%.

[0038] Furthermore, the resin that forms the main component of the other resin layers can be the same polyester resin as the polyester heat shrink film, or preferably at least one of the following: acrylic resin, olefin resin, urethane resin, rubber resin, etc., which are different from it.

[0039] Furthermore, it is preferable to fabricate the polyester heat-shrinkable film into a multi-layer structure to further achieve the effect of preventing hydrolysis and providing physical protection, or as... Figure 1 As shown in (c), a shrinkage rate adjustment layer 10c is provided on the surface of the polyester heat shrink film 10 so that the shrinkage rate of the polyester heat shrink film remains uniform in the plane. This shrinkage adjustment layer can be laminated using adhesives, coating methods, or heat treatment, depending on the shrinkage characteristics of the polyester heat shrink film.

[0040] More specifically, the thickness of the shrinkage adjustment layer is in the range of 0.1~3μm. When the shrinkage rate of the polyester heat shrink film at a specified temperature is too large, it is preferable to laminate a shrinkage adjustment layer of the type that suppresses the excessive shrinkage rate. Furthermore, when the shrinkage rate of the polyester heat-shrinkable film at a specified temperature is too low, it is preferable to laminate a shrinkage rate adjustment layer of the type that increases the shrinkage rate. Therefore, as a polyester-based heat shrink film, it is not about making various heat shrink films with different shrinkage rates, but about using a shrinkage rate adjustment layer to obtain the desired shrinkage rate.

[0041] (4) Other 2 Next, it was mentioned Figure 6 and Figure 7 The paper provides a detailed explanation of the wrinkle resistance of polyester heat-shrinkable film used as a tubular label when it is installed on PET bottles. Right now, Figure 6 This is a photograph showing the appearance of the cylindrical label without wrinkles, corresponding to Example 1. Figure 6 Image (a) shows the entire bottle body covered by the cylindrical label. Furthermore, Figure 6 (b)~(d) in the text are to Figure 6 The enlarged diagrams shown in (a) of the bottle body are of the upper (region P), middle (region Q) and lower (region R) parts, respectively, and it is assumed that no wrinkles are produced in any part of the upper to lower parts. on the other hand, Figure 7 This is a photograph showing the appearance of the cylindrical label in the case of wrinkling, which is equivalent to Comparative Example 1. Figure 7 Image (a) shows the entire bottle body covered by the cylindrical label. Furthermore, Figure 7 (b)~(d) in the text are to Figure 7 The enlarged diagrams shown in (a) of the bottle body are of the upper (region S), middle (region T), and lower (region U) parts, respectively, and it is assumed that wrinkles are generated in any part from the upper to the lower. In addition, according to Figure 7 In (c), it can be assumed that the plastic bottle itself also deformed in the middle part (region T) of the bottle body.

[0042] [Second Implementation Plan] The second embodiment is a method for manufacturing a polyester heat shrink film, which is a method for manufacturing a polyester heat shrink film derived from the dicarboxylic acid compound and diol compound of the first embodiment, characterized by having the following steps 1 to 2. Step 1: The process of preparing dicarboxylic acid compounds and diol compounds as reactants and reacting them to prepare polyester resins. Step 2: A step of manufacturing a polyester heat shrink film having the following structures (a) to (d) by stretching a polyester resin along a specified direction. (a) When the thermal shrinkage rate in the main shrinkage direction is defined as A1 when shrinkage is performed in warm water at 80°C for 10 seconds, A1 is set to a value in the range of 21% to 65%. (b) When the thermal shrinkage rate in the direction orthogonal to the main shrinkage direction is defined as A2 when shrinking in warm water at 80°C for 10 seconds, A2 is set to a value in the range of -5 to 10%. (c) Set the absolute value of the ratio of heat shrinkage rates A1 to A2 (A1 / A2) to a value of 5.5 or higher. (d) The necking rate measured under the conditions of 70°C in warm water for 10 seconds is set to a value of 6% or less. The manufacturing method of the polyester heat shrink film according to the second embodiment will be described in detail below, with appropriate reference to the accompanying drawings.

[0043] 1. Raw material preparation and mixing process First, select crystalline polyester resin, amorphous polyester resin, rubber-based resin, antistatic agent, anti-hydrolysis agent and other main agents and additives as raw materials. Next, preferably, while weighing the prepared crystalline polyester resin or amorphous polyester resin in a mixing container, the resin is mixed and stirred until homogeneous using a stirring device.

[0044] 2. Raw material sheet manufacturing process Next, the uniformly mixed raw materials are preferably dried to an absolutely dry state. Next, as a typical example, extrusion molding is preferred to produce raw material sheets of a specified thickness. More specifically, for example, by extrusion molding at an extrusion temperature of 245°C using an extruder (manufactured by TANABE PLASTICS MACHINERY CO.,LTD.) with an L / D of 24 and an extrusion screw diameter of 50 mm, raw material sheets of a specified thickness (typically 30~1000 μm) can be obtained.

[0045] 3. Fabrication of Polyester-Based Heat Shrink Film Next, the obtained raw material sheet is heated and extruded using a heat shrink film manufacturing device while being moved on or between rollers, thereby producing a polyester heat shrink film. That is, preferably, the film width is substantially expanded by using a specified preheating temperature, stretching temperature, heat-fixing temperature and stretching ratio described later, while heating and extruding, and stretching in a specified direction at the same time, thereby causing the polyester molecules constituting the polyester heat shrink film to crystallize into a specified shape. Then, by solidifying it in this state, it is possible to produce a heat-shrinkable polyester heat-shrinkable film that can be used as decoration or label, etc. In addition, when manufacturing heat shrink film, it is possible to stretch the film not only by so-called transverse stretching (stretching process along the TD direction), but also by longitudinal stretching (stretching process along the MD direction). That is, in the case of the present invention, even if the stretching process is performed in any direction and that direction is taken as the main shrinkage direction, the heat shrinkage rate A1, A2, absolute value (A1 / A2), necking rate and heat shrinkage stress (C) can be limited to values ​​within a specified range, thereby suppressing the generation of fine wrinkles.

[0046] (1) Stretch ratio in the MD direction Furthermore, when performing so-called transverse stretching, it is generally preferable to set the stretch ratio in the MD direction of the polyester heat-shrinkable film before heat shrinking (sometimes referred to as the average MD stretch ratio, or simply the MD stretch ratio) to a value in the range of 100% to 200%. The reason is that by specifically limiting the stretch ratio in the MD direction to a value within a specified range as described above, the generation of fine wrinkles can be suppressed when the heat-shrinkable film is heat-shrinked. More specifically, if the stretch ratio in the MD direction is less than 100%, it can sometimes make it difficult to limit the heat shrinkage rates A1, A2, absolute values ​​(A1 / A2), necking rate, and heat shrinkage stress (C), resulting in a significant decrease in production output during manufacturing. On the other hand, if the stretch ratio in the MD direction is greater than 200%, it may sometimes affect the shrinkage rate in the TD direction, and the adjustment of its shrinkage rate itself becomes difficult. Therefore, it is more preferable to set the stretch ratio in the MD direction to a value in the range of 110 to 180%, and even more preferably to set it to a value in the range of 120 to 160%. In addition, when performing so-called longitudinal stretching, it is preferable to set the stretching ratio in the MD direction to a value in the range of 300 to 600%, and more preferably to a value in the range of 400 to 500%.

[0047] (2) Stretch ratio in the TD direction Furthermore, as a preferred embodiment, the stretch ratio in the TD direction of the polyester heat-shrinkable film before heat shrinking (sometimes referred to as the average TD stretch ratio, or simply the TD stretch ratio) is set to a value in the range of 300% to 600%. The reason is that, not only the stretching ratio in the MD direction mentioned above, but also the stretching ratio in the TD direction is specifically limited to a specified range, and the heat shrinkage rates A1, A2, absolute value (A1 / A2), necking rate and heat shrinkage stress (C) are specifically limited to a specified range, which can further suppress the generation of fine wrinkles.

[0048] More specifically, if the stretch ratio in the TD direction is less than 300%, the shrinkage rate in the TD direction will sometimes decrease significantly, and the application of the polyester heat shrink film will be excessively limited. On the other hand, if the TD stretch ratio becomes greater than 600%, the heat shrinkage rate will sometimes increase significantly, which will overly limit the application of polyester heat shrink film or make it difficult to control its stretch ratio within a certain range. Therefore, it is more preferable to set the TD stretch ratio to a value in the range of 350 to 550%, and even more preferable to set it to a value in the range of 400 to 500%. In addition, when performing so-called longitudinal stretching, it is preferable to set the stretching ratio in the TD direction to a value in the range of 100 to 200%, and more preferably to a value in the range of 110 to 180%.

[0049] 4. Inspection procedures for polyester heat shrink film For the produced polyester heat shrink film, it is preferable to continuously or intermittently measure the following characteristics and set up a prescribed inspection procedure. That is, by conducting a prescribed inspection process, measuring the following characteristics, and confirming that the values ​​are within the prescribed range, it is possible to produce a polyester heat shrink film with more uniform shrinkage characteristics. 1) Visually inspect the appearance of the polyester heat shrink film. 2) Deviation in thickness measurement 3) Determine the tensile modulus of elasticity 4) Determine tear strength 5) Determining viscoelastic properties based on SS curves

[0050] Furthermore, for manufacturing the polyester heat-shrinkable film of the second embodiment, it is important to at least measure the following components (a) to (d) and confirm that they are within the specified range. (a) When the thermal shrinkage rate in the main shrinkage direction is defined as A1 when shrinkage is performed in warm water at 80°C for 10 seconds, A1 is set to a value in the range of 21% to 65%. (b) When the thermal shrinkage rate in the direction orthogonal to the main shrinkage direction is defined as A2 when shrinking in warm water at 80°C for 10 seconds, A2 is set to a value in the range of -5 to 10%. (c) Set the absolute value of the ratio of heat shrinkage rates A1 to A2 (A1 / A2) to a value of 5.5 or higher. (d) The necking rate measured under the conditions of 70°C in warm water for 10 seconds is set to a value of 6% or less.

[0051] [Third Implementation Plan] The third implementation plan is an implementation plan related to the method of using polyester heat shrink film. Therefore, all known methods of using heat shrink film can be appropriately applied. For example, when implementing the method of using polyester heat shrink film, firstly, the polyester heat shrink film is cut into appropriate lengths and widths to form long cylindrical objects. Next, the long cylindrical object is fed to an automatic labeling machine (shrink labeler) and further cut into the necessary length. Next, it is embedded in the outside of a PET bottle or similar container filled with contents.

[0052] Next, the polyester heat-shrinkable film, which is embedded on the outside of PET bottles, is subjected to heat treatment by passing it through a hot air channel or steam channel at a specified temperature. Then, radiant heat such as infrared rays or heating steam at around 90°C, which are present in the aforementioned channels, are blown from all sides to uniformly heat the polyester heat-shrinkable film, thereby causing it to heat-shrink. This allows it to fit tightly onto the outer surface of PET bottles and other containers, enabling the rapid production of labeled containers.

[0053] Hereinafter, the polyester heat-shrinkable film according to the invention, as detailed in the first embodiment, is characterized by at least satisfying the configurations (a) to (d). In this way, even when placed under high humidity conditions for a short period of time, changes in physical properties caused by moisture absorption can be prevented, and the specified heat shrinkage rate can be obtained with good reproducibility at various heat treatment temperatures. Therefore, even if the values ​​of heat shrinkage rate, etc., deviate slightly, the cause of the specified influencing factors can be mitigated, and the uneven shrinkage caused by the rapid thermal response in the polyester heat shrink film during heat shrinkage can be suppressed, and the formation of fine wrinkles can also be suppressed.

[0054] Therefore, as Figure 6 As shown in (a) to (d), even if the label made of the heat-shrinkable film is draped over the bottle body and heat-shrinked, it can be installed in a way that follows the shape of the bottle, and further, the generation of fine wrinkles can be suppressed. However, when the polyester heat-shrinkable film does not meet the requirements of (a) to (d), it will be as follows: Figure 7 As shown in (a) to (d), uneven shrinkage of the heat-shrinkable film occurs from the upper part to the lower part of the bottle body, and wrinkles and deformation of the bottle are clearly observed. Example

[0055] The present invention will now be described in detail based on embodiments. Unless otherwise specified, the scope of the present invention is not limited to the descriptions of the embodiments, etc. In addition, the polyester resins used in the examples are shown below.

[0056] (PET1) A polyester resin composed of dicarboxylic acid and diol, wherein the dicarboxylic acid is 100 mol% terephthalic acid; and the diol is 69 mol% ethylene glycol, 6 mol% diethylene glycol, and 25 mol% 1,4-cyclohexanediethanol.

[0057] (PET2) A polyester resin composed of dicarboxylic acid and diol, wherein the dicarboxylic acid is 100 mol% terephthalic acid; and the diol is 58 mol% ethylene glycol, 5 mol% diethylene glycol, 27 mol% 1,4-cyclohexanediethanol, and 10 mol% 1,4-butanediol.

[0058] (PET3) A polyester resin composed of dicarboxylic acid and diol, wherein the dicarboxylic acid is 100 mol% terephthalic acid; and the diol is 68 mol% ethylene glycol, 12 mol% diethylene glycol, and 20 mol% 1,4-cyclohexanediethanol.

[0059] (PET4) A polyester resin composed of dicarboxylic acid and diol, wherein the dicarboxylic acid is 100 mol% terephthalic acid; and the diol is 74 mol% ethylene glycol, 5 mol% diethylene glycol, and 21 mol% 1,4-cyclohexanediethanol.

[0060] (PET5) A polyester resin composed of dicarboxylic acid and diol, wherein the dicarboxylic acid is 100 mol% terephthalic acid; and the diol is 70 mol% ethylene glycol, 2 mol% diethylene glycol, and 28 mol% 1,4-cyclohexanediethanol.

[0061] (PET6) A polyester resin composed of dicarboxylic acid and diol, wherein the dicarboxylic acid consists of 79 mol% terephthalic acid and 21 mol% isophthalic acid; and the diol consists of 85 mol% ethylene glycol, 2 mol% diethylene glycol, and 13 mol% neopentyl glycol.

[0062] (additive) A silica masterbatch (manufactured by Sumika Color Co., Ltd., trade name "EPM-7E325") is composed of silica with a silica content of 5% by weight relative to 100% by weight of matrix resin (PET resin) and an average silica particle size of 2.7 μm.

[0063] [Example 1] 1. Fabrication of polyester heat shrink film Amorphous polyester (PET1) in 100 parts by weight and additives (silica particles) as anti-caking agents in 1 part by weight are placed in a mixing container and mixed evenly to form the raw material. Next, after the raw material is made into an absolutely dry state, it is extruded at an extrusion temperature of 260°C using an extruder with an L / D of 24 and an extrusion screw diameter of 50 mm (manufactured by TANABE PLASTICS MACHINERY CO.,LTD.) to obtain a raw material sheet with a thickness of 150 μm. Next, using a heat shrink film manufacturing device, longitudinal stretching is performed at a preheating temperature of 95°C, a stretching temperature of 85°C, a heat setting temperature of 84°C, and a stretching ratio of 100% in the MD direction and 530% in the TD direction to produce a polyester heat shrink film with a thickness of 30μm from the raw material sheet.

[0064] 2. Evaluation of Polyester-Based Heat Shrink Film (1) Evaluation 1: Thermal shrinkage rate A1 For the obtained polyester heat shrink film, the heat shrinkage rate (A1) in the main shrinkage direction was measured when it was shrunk in warm water at 80°C for 10 seconds, and evaluated according to the following criteria. ◎: The heat shrinkage rate (A1) is a value in the range of 30~50%. 〇: The heat shrinkage rate (A1) is a value in the range of 21% or more and less than 30%, or a value in the range of 50% or more and less than 65%. △: The heat shrinkage rate (A1) is a value in the range of 16% or more and less than 21%, or a value in the range of 65% or more and less than 70%. ×: The heat shrinkage rate (A1) is less than 16% or greater than 70%.

[0065] (2) Evaluation 2: Thermal shrinkage rate A2 For the obtained polyester heat shrink film, the heat shrinkage rate (A2) in the direction orthogonal to the main shrinkage direction was measured when it was shrunk in warm water at 80°C for 10 seconds, and evaluated according to the following criteria. ◎: The heat shrinkage rate (A2) is a value within the range of -3% to 5%. 〇: The heat shrinkage rate (A2) is a value in the range of -5% or more and less than -3%, or a value in the range of greater than 5% and less than 10%. △: The heat shrinkage rate (A2) is a value in the range of -10% or more and less than -5%, or a value in the range of more than 10% and less than 12%. ×: The heat shrinkage rate (A2) is a value less than -10% or greater than 12%.

[0066] (3) Evaluation 3: Neck retraction rate For the obtained polyester heat shrink film, the necking rate was measured under the condition of fixing the main shrinkage direction and in warm water at 70°C for 10 seconds, and evaluated according to the following criteria. That is, the polyester heat shrink film 10 is cut into pieces such as... Figure 8 The strip shown in (a) is 200 mm in the main contraction direction and 100 mm in the orthogonal direction, and is used as the test sample. In addition, a mark is pre-drawn along the orthogonal direction at the center of the main shrinkage direction of the test sample, and the length of the mark is set as L0. Next, the test sample is mounted as follows: Figure 8In the case shown in (b), the two ends of the test specimen are fixed on a fixed frame fixture with an internal dimension of 140 mm in length and 140 mm in width, with the main shrinkage direction aligned with the internal dimension length direction. That is, the specimen is installed such that the two ends of the test specimen in the main shrinkage direction are fixed to the fixed frame fixture. On the other hand, the elongated test specimen is arranged and fixed in such a way that a specified space can be formed between the fixed frame fixture and the two sides of the orthogonal direction of the elongated test specimen. Next, as follows Figure 8 The test specimen shown in (c) is mounted on a fixed frame fixture and immersed in warm water at 70°C for 10 seconds, and then immersed in water at 30°C or below for 10 seconds, thereby determining the maximum thermal shrinkage rate in the orthogonal direction based on the change in the length of the markings on the test specimen. Finally, according to the following formula (1), the value obtained by dividing the obtained thermal shrinkage rate by 2 is taken as the necking rate. Necking rate (%) = (L0 - L) / 2L0 × 100 (1) L0: Length of the markings on the sample before heat treatment. L: Length of the markings on the test specimen after heat treatment

[0067] ◎: The value of the neck contraction rate is within the range of 0 to 4%. 〇: The neck contraction rate is a value within the range of greater than 4% and less than 6%. △: The neck contraction rate is a value within the range of greater than 6% and less than 8%. ×: The neck retraction rate is greater than 8%.

[0068] (4) Evaluation 4: Absolute value (A1 / A2) For the obtained polyester heat shrink film, the absolute value (A1 / A2) is calculated and evaluated according to the following criteria. ◎: The absolute value (A1 / A2) is a value in the range of 10 to 100. 〇: The absolute value (A1 / A2) is a value in the range of 5.5 or higher and less than 10, or a value in the range of 100 or higher and less than 110. △: The absolute value (A1 / A2) is a value in the range of 4.5 or higher and less than 5.5, or a value in the range of 110 or higher and less than 120. ×: The absolute value (A1 / A2) is less than 4.5 or greater than 120.

[0069] (5) Evaluation 5: Maximum shrinkage stress (C) The obtained polyester heat shrink film was cut into short strips with a width of 25.4 mm along the MD direction and a length of 75 mm along the TD direction, and these were used as test pieces. Next, the shrinkage stress of the test piece was measured using a strength and ductility testing machine equipped with a heating furnace. More specifically, preheat the furnace to 85°C, temporarily stop the air supply to the furnace, open the furnace door, install the test piece on the fixture of the strength and ductility tester, then quickly close the furnace door and restart the air supply. Next, the shrinkage stress is measured for more than 30 seconds, and the maximum value measured is taken as the maximum shrinkage stress (C). The stress is then evaluated according to the following criteria. ◎: The maximum shrinkage stress (C) is a value in the range of 4~8MPa. 〇: The maximum shrinkage stress (C) is a value in the range of 3 MPa or more and less than 4 MPa, or a value in the range of 8 MPa or more and less than 10 MPa. △: The maximum shrinkage stress (C) is a value in the range of 2 MPa or more and less than 3 MPa, or a value in the range of 10 MPa or more and less than 12 MPa. ×: The maximum shrinkage stress (C) is a value less than 2 MPa or greater than 12 MPa.

[0070] (6) Evaluation 6: Anti-wrinkle properties Prepare commercially available cylindrical PET bottles (500ml) filled with beverage water. Next, on the strip heat shrink film obtained by cutting the polyester heat shrink film into a strip 26cm wide, 1mm wide perforations are set along the long side, and 1,3-dioxolane is coated on the end in the width direction. Next, the ends in the width direction are overlapped and glued together with an overlap of about 1 cm to form a cylindrical label with a diameter of about 8 cm. Further, the cylindrical label is cut every 16 cm along its long side to obtain multiple cylindrical labels. Next, the cylindrical label is draped over the body of the prepared cylindrical PET bottle, placed on a conveyor belt, and simultaneously moved at a speed of 6 m / min through a steam channel maintained at 85°C, so that the cylindrical label is heat-shrinked in a way that it fits tightly against the body of the cylindrical PET bottle from top to bottom. Finally, the heat-shrinked tubular label was visually inspected, and its wrinkle resistance was evaluated based on whether wrinkles of a specified length (more than 1 cm) or a specified width (more than 1 mm) were produced, according to the following criteria. ◎: Of the 5 tubular labels, none of them showed the required wrinkles. 〇: Of the 5 tubular labels, no prescribed wrinkles were observed in 3 or more. △: Of the 5 tubular labels, more than 1 did not show the required wrinkles. ×: Of the 5 tubular labels, all 5 were found to have produced the prescribed wrinkles.

[0071] [Example 2] In Example 2, as shown in Table 1, PET1 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to limit the process, the manufacturing conditions during longitudinal stretching were changed. That is, in Example 2, a polyester heat shrink film with a thickness of 40 μm was made from raw material sheet by using a preheating temperature of 105°C, a stretching ratio of 100% in the MD direction and 500% in the TD direction, a stretching temperature of 88°C, and a heat setting temperature of 75°C. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0072] [Example 3] In Example 3, as shown in Table 1, PET2 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to limit the process, the manufacturing conditions during longitudinal stretching were changed. That is, a polyester heat shrink film with a thickness of 25μm is manufactured from raw material sheet by preheating at 90℃, stretching ratio of 100% in the MD direction and 515% in the TD direction, stretching temperature of 90℃, and heat setting temperature of 80℃. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0073] [Example 4] In Example 4, as shown in Table 1, PET3 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to limit the process, the manufacturing conditions during longitudinal stretching were changed. That is, a polyester heat shrink film with a thickness of 40μm is manufactured from raw material sheet by preheating at a temperature of 90℃, stretching ratio of 400% in the MD direction and 100% in the TD direction, stretching temperature of 82℃, and heat setting temperature of 80℃. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0074] [Example 5] In Example 5, as shown in Table 1, PET4 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to limit the process, the manufacturing conditions during longitudinal stretching were changed. That is, a polyester heat shrink film with a thickness of 45μm is manufactured from raw material sheet by preheating at 84℃, stretching ratio of 400% in the MD direction and 100% in the TD direction, stretching temperature of 84℃, and heat setting temperature of 75℃. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0075] [Example 6] In Example 6, as shown in Table 1, PET4 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to limit the process, the manufacturing conditions during longitudinal stretching were changed. That is, a polyester heat shrink film with a thickness of 50μm is manufactured from raw material sheet by preheating at a temperature of 97℃, stretching ratio of 400% in the MD direction and 100% in the TD direction, stretching temperature of 93℃, and heat setting temperature of 88℃. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0076] [Example 7] In Example 7, as shown in Table 1, PET1 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to limit the process, the manufacturing conditions during longitudinal stretching were changed. That is, a polyester heat shrink film with a thickness of 45μm is manufactured from raw material sheet by preheating at a temperature of 70℃, stretching ratio of 420% in the MD direction and 100% in the TD direction, stretching temperature of 85℃, and heat setting temperature of 83℃. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0077] [Comparative Example 1] In Comparative Example 1, as shown in Table 1, PET5 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to impose restrictions, the manufacturing conditions during longitudinal stretching were changed. That is, a polyester heat shrink film with a thickness of 45μm is manufactured from raw material sheet by setting the preheating temperature to 75℃, the stretching ratio to 100% in the MD direction and 500% in the TD direction, the stretching temperature to 75℃, and the heat setting temperature to 50℃. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0078] [Comparative Example 2] In Comparative Example 2, as shown in Table 1, PET6 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to impose restrictions, the manufacturing conditions were changed. That is, a polyester heat shrink film with a thickness of 47μm is manufactured from raw material sheet by setting the preheating temperature to 75℃, the stretching ratio to 100% in the MD direction and 500% in the TD direction, the stretching temperature to 75℃, and the heat setting temperature to 50℃. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0079] [Comparative Example 3] In Comparative Example 3, as shown in Table 1, PET6 was used as the polyester resin, and the values ​​of components (a) to (d) were changed. In order to impose restrictions, the manufacturing conditions were changed. That is, a polyester heat shrink film with a thickness of 42μm is manufactured from raw material sheet by setting the preheating temperature to 90℃, the stretching ratio to 100% in the MD direction and 500% in the TD direction, the stretching temperature to 90℃, and the heat setting temperature to 60℃. Then, the wrinkle resistance and other properties of the prepared polyester heat-shrinkable film were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0080] [Table 1]

[0081] [Table 2] Industrial applicability

[0082] The polyester heat-shrinkable film according to the present invention, having at least the following configurations (a) to (d), can stably undergo heat shrinkage and exhibit excellent wrinkle resistance even when applied to various PET bottles, etc. (a) The thermal shrinkage rate A1 in the main shrinkage direction when shrinking in warm water at 80°C for 10 seconds is set to a value in the range of 21% to 65%. (b) The thermal shrinkage rate A2 in the direction orthogonal to the main shrinkage direction when shrinking in warm water at 80°C for 10 seconds is set to a value in the range of -5 to 10%. (c) Set the absolute value of the ratio of heat shrinkage rates A1 to A2 (A1 / A2) to a value of 5.5 or higher. (d) The necking rate measured under the conditions of 70°C in warm water for 10 seconds is set to a value of 6% or less.

[0083] Furthermore, according to the method for manufacturing polyester heat shrink film of the present invention, by manufacturing polyester heat shrink film having at least the following components (a) to (d) using a prescribed process, it is possible to effectively obtain polyester heat shrink film that can stably undergo heat shrinkage and exhibit excellent wrinkle resistance even when applied to various PET bottles, etc.

[0084] That is, the polyester heat shrink film and the like according to the present invention not only have a heat shrinkage rate (A1 and A2) under specified conditions, but also a neck shrinkage rate under specified conditions, so that even when applied to PET bottles with complex shapes, it can stably perform heat shrinkage and exhibit excellent wrinkle resistance. Therefore, its wide range of applications has been significantly expanded due to its suitability for use in various PET bottles and lunch boxes as outer packaging materials, making it highly practical for industrial applications. Explanation of reference numerals in the attached figures

[0085] 10: Polyester heat shrink film; 10a: Other resin layer 1; 10b: Other resin layer 2; 10c: Shrinkage adjustment layer.

Claims

1. A polyester-based heat-shrinkable film, which is a polyester-based heat-shrinkable film derived from polyester resin, characterized in that, It has the following components (a) to (d): (a) When the thermal shrinkage rate in the main shrinkage direction is defined as A1, and the shrinkage is carried out in warm water at 80°C for 10 seconds, A1 is set to a value in the range of 21% to 65%. (b) When the thermal shrinkage rate in the direction orthogonal to the main shrinkage direction is defined as A2, and the shrinkage is carried out in warm water at 80°C for 10 seconds, A2 is set to a value in the range of -5% to 10%. (c) Set the absolute value (A1 / A2) of the ratio of the heat shrinkage rates A1 to A2 to a value of 5.5 or higher. (d) The necking rate measured under the conditions of 70°C in warm water for 10 seconds is set to a value of 6% or less.

2. The polyester-based heat-shrinkable film according to claim 1, characterized in that, When the maximum shrinkage stress in the main shrinkage direction at a shrinkage temperature of 85°C is set as C, C is set to a value in the range of 3 to 10 MPa.

3. The polyester-based heat-shrinkable film according to claim 1, characterized in that, The thickness of the polyester heat-shrinkable film is set to a value in the range of 10~100μm.

4. The polyester-based heat-shrinkable film according to claim 1, characterized in that, The main shrinkage direction of the polyester heat shrink film is the MD direction.

5. The polyester-based heat-shrinkable film according to claim 1, characterized in that, The polyester resin is derived from dicarboxylic acid compounds and diol compounds that are reactants, and the diol compounds include at least ethylene glycol, diethylene glycol and 1,4-cyclohexanediethanol.

6. A method for manufacturing a polyester heat-shrinkable film, comprising a method for manufacturing a polyester resin film derived from a dicarboxylic acid compound and a diol compound as reactants, characterized in that, It has the following processes 1 to 2: Step 1: The step of preparing the dicarboxylic acid compound and diol compound as the reaction components and reacting them to prepare polyester resin; Step 2: A step of manufacturing a polyester heat-shrinkable film having the following structures (a) to (d) by stretching the polyester resin along a specified direction. (a) When the thermal shrinkage rate in the main shrinkage direction is defined as A1, and the shrinkage is carried out in warm water at 80°C for 10 seconds, A1 is set to a value in the range of 21% to 65%. (b) When the thermal shrinkage rate in the direction orthogonal to the main shrinkage direction is defined as A2, and the shrinkage is carried out in warm water at 80°C for 10 seconds, A2 is set to a value in the range of -5% to 10%. (c) Set the absolute value (A1 / A2) of the ratio of the heat shrinkage rates A1 to A2 to a value of 5.5 or higher. (d) The necking rate measured under the conditions of 70°C in warm water for 10 seconds is set to a value of 6% or less.

7. The method for manufacturing a polyester heat-shrinkable film according to claim 6, characterized in that, In step 2, the polyester heat shrink film is stretched along the MD direction, which is the specified direction.

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