Polyester heat-shrinkable film and method for manufacturing polyester heat-shrinkable film

Abstract

The present invention provides polyester-based heat-shrinkable films with excellent wrinkle resistance, even when applied to drug containers, dry cell batteries, tapes, etc. [Solution] In a polyester heat-shrinkable film, when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction, (a) the 2θ value of the XRD includes a crystal peak that shows the maximum value at a predetermined diffraction angle of the (-10⁵) plane, and the full width at half maximum of the crystal peak is 6° or less, the crystallite size measured by XRD is 3.2 nm or less, the heat shrinkage rate A1 in the MD direction at 80°C for 30 seconds is in the range of 15 to 60%, and the refractive index in the TD direction is in the range of 1.55 to 1.60.

Description

Technical Field

[0001] The present invention relates to a polyester-based heat-shrinkable film having the MD direction as the main shrinkage direction and a method for manufacturing the polyester-based heat-shrinkable film. More specifically, in order to correspond to various containers and the like, so-called longitudinal stretching is performed, and the half-value width of the crystal peak and the like are controlled using an X-ray diffractometer (hereinafter sometimes referred to as XRD), and heat shrinkage is performed with high accuracy and quantification. The present invention relates to a polyester-based heat-shrinkable film having the MD direction as the main shrinkage direction (hereinafter sometimes simply referred to as a heat-shrinkable film) and an efficient manufacturing method thereof.

Background Art

[0002] Conventionally, heat-shrinkable films are widely used not only as PET bottles but also as base films for labels such as dry batteries and tapes, and are composed of various materials including polyester resins. These heat-shrinkable films are heat-shrunk by passing through a tunnel that generates hot air or steam and are attached to containers, but shrinkage differences (non-uniformity) may occur during heat shrinkage, resulting in the occurrence of wrinkles and color non-uniformity. Therefore, various heat-shrinkable films have been proposed to prevent the occurrence of shrinkage differences (non-uniformity) and the occurrence of wrinkles and color non-uniformity during heat shrinkage.

[0003] For example, a polyester-based heat-shrinkable film has been proposed that has a high heat shrinkage rate in the TD direction (width direction), a small heat shrinkage rate in the MD direction (length direction), high mechanical strength in the length direction, good perforation sealability, and excellent shrinkage finish (see Patent Document 1). More specifically, it is composed of a polyester resin, and the polyester resin has a ratio (A mol%) of an acid component other than terephthalic acid in the total acid component and a ratio (B mol%) of an alcohol component other than ethylene glycol in the total alcohol component, and 5 mol% ≤ A + B ≤ 40 mol%. Furthermore, the polyester-based heat-shrinkable film is characterized by containing 1 to 30 mol% of naphthalenedicarboxylic acid and 0.3 to 3 mol% of an alkali metal salt of sulfobenzenedicarboxylic acid in the total acid components.

[0004] Furthermore, a polyester heat-shrinkable film has been proposed that strictly controls the amount of amorphous components in the total polyester resin components, and limits the hot water shrinkage rate at 80°C and 90°C in the longitudinal direction of the film, as well as the hot water shrinkage rate at 90°C in the width direction of the film (see Patent Document 2). More specifically, it has ethylene terephthalate as its main component and contains one or more monomer components that can become amorphous components in the total polyester resin components, with their total amount being 15 mol% or more. Furthermore, the polyester heat shrinkable film is characterized by a hot water shrinkage rate of 30% or more in the longitudinal direction (MD direction) at a processing temperature of 80°C and a processing time of 10 seconds, and 40% or more at a processing temperature of 90°C and a processing time of 10 seconds, while the hot water shrinkage rate in the width direction (TD direction) is 10% or less at 90°C and a processing time of 10 seconds.

[0005] Furthermore, a heat-shrinkable polyester film has been proposed that is less prone to insufficient shrinkage and shrinks primarily in the longitudinal direction (MD direction) of the film (see Patent Document 3). More specifically, the heat-shrinkable polyester film is derived from amorphous polyester resin and does not exhibit a peak in the endothermic curve during film melting point measurement using differential scanning calorimetry (DSC), and is formed by first stretching the film by more than twice its width in the film width direction, and then stretching it by more than twice its length in the film longitudinal direction during the film manufacturing stretching process. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 08-027259 (Claims, etc.) [Patent Document 2] Japanese Patent Publication No. 2007-016120 (Claims, etc.) [Patent Document 3] Japanese Patent Publication No. 2015-34061 (Claims, etc.) [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in all of the heat-shrinkable films described in Patent Documents 1 to 3, while the rate of heat shrinkage at a predetermined temperature and in a predetermined shrinkage direction is limited to a predetermined range, no consideration was given to controlling the full width at half maximum of the crystal peaks measured by an X-ray diffraction (XRD) device. Therefore, in the case of various containers where the diameter of the bottle body is not uniform, and in some parts the horizontal cross-sectional shape of the body is not circular but has a complex shape, the thermal shrinkage tends to be uneven, making it difficult to suppress the occurrence of fine wrinkles accurately and quantitatively.

[0008] Therefore, the inventors of the present invention have found that by limiting the full width at half maximum and crystallite size of the crystal peak corresponding to the (-10⁵) plane to values ​​within a predetermined range using XRD measurements, the main shrinkage direction is the MD direction, and even when applied to various containers, the occurrence of wrinkles can be suppressed accurately and quantitatively, thus completing the present invention. In other words, the present invention aims to provide a polyester heat-shrinkable film that exhibits excellent wrinkle resistance when installed, even when applied to the coating of drug containers, dry cell batteries, tapes, etc., where the main shrinkage direction is the MD direction and the film is applied to the entire surface from above along the vertical direction before being heat-shrinked, and to provide an efficient method for manufacturing such a heat-shrinkable film. [Means for solving the problem]

[0009] According to the present invention, a polyester heat-shrinkable film derived from a polyester resin is provided, characterized in that when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction, the following configurations (a) to (c) are satisfied, thereby solving the above problems. (a) The 2θ value obtained by an X-ray diffraction analyzer (usually an XRD as a transmission X-ray diffraction analyzer; the same applies hereinafter) includes a crystal peak (including a crystalline domain; the same applies hereinafter) that shows the maximum value at the diffraction angle of the (-10⁵) plane (in the range of 42° or more to less than 44°), and the full width at half maximum of the crystal peak is 6° or less. (b) The crystallite size of the (-10⁵) plane obtained by the X-ray diffraction analyzer shall be 3.2 nm or less. (c) When the thermal shrinkage rate in the MD direction is A1 under shrinkage conditions of 80°C for 30 seconds, A1 shall be a value within the range of 15 to 60%. In other words, by using XRD, a simple yet precise measurement method, the full width at half maximum and crystallite size of a predetermined crystal peak can be accurately limited, and by satisfying configurations (a) to (c), it can be suitably applied to various containers in which a polyester heat-shrinkable film is typically mounted vertically and then heat-shrinked. Therefore, even when suitable for use as outer packaging for drug containers, dry cell batteries, tapes, etc., polyester heat-shrinkable films that effectively suppress wrinkle formation during application can be efficiently manufactured.

[0010] In constructing the polyester-based heat-shrinkable film of the present invention, it is preferable that the following configuration (d) is satisfied. (d) The refractive index in the TD direction shall be within the range of 1.55 to 1.60. By limiting the refractive index in the TD direction in this way, the full width at half maximum of the crystal peaks and the crystallite size can be determined with greater precision. Consequently, even when applied to various containers, the occurrence of fine wrinkles can be suppressed with greater precision and quantitative accuracy.

[0011] In constructing the polyester-based heat-shrinkable film of the present invention, it is preferable that the following configuration (e) is satisfied. (e) When the thermal shrinkage rate is A2 when the heat shrinkage is performed in the MD direction under shrinkage conditions of 70°C for 30 seconds, the value of A2 shall be within the range of 1 to 35%. By limiting the thermal shrinkage rate A2 in the MD direction in this way, it is possible to apply this material to various containers and other items, and even when applying a wide range of thermal shrinkage temperatures, the occurrence of fine wrinkles and other defects can be suppressed with greater precision.

[0012] In constructing the polyester-based heat-shrinkable film of the present invention, it is preferable that the following configuration (f) is satisfied. (f) When the thermal shrinkage rate is A3 when the heat shrinkage is performed in the MD direction under the shrinkage conditions of 100℃ for 30 seconds, the value of A3 shall be within the range of 25 to 80%. By limiting the heat shrinkage coefficient A3 in the MD direction in this way, it is possible to apply this material to various containers and other items, and even when a wide range of heat shrinkage temperatures are applied, the occurrence of fine wrinkles and other defects can be suppressed with greater precision.

[0013] In constructing the polyester-based heat-shrinkable film of the present invention, it is preferable that the following configuration (g) is satisfied. (g) The haze value measured in accordance with JIS K 7136:2000 shall be 10% or less. By controlling the haze value (film thickness: 25-50 μm) within a predetermined range, it is possible to achieve not only excellent transparency but also superior printability and uniform heat shrinkage.

[0014] In constructing the polyester-based heat-shrinkable film of the present invention, it is preferable that the following configuration (h) is satisfied. (h) It is preferable that the neck-in ratio measured under the condition of being in 70°C hot water for 10 seconds be a value of 4% or less. By limiting the neck-in rate in this way, excellent wrinkle resistance can be achieved even when applied to various types of PET bottles, drug containers, batteries, tapes, etc.

[0015] In forming the polyester-based heat-shrinkable film of the present invention, it is preferable that the thickness be a value within the range of 10 to 100 μm. By restricting the thickness in this way, handling and production management become easier, and when applied to various containers and the like, even when the heat shrinkage temperature varies somewhat, the occurrence of fine wrinkles and the like can be suppressed.

[0016] Another aspect of the present invention is a method for producing a polyester-based heat-shrinkable film derived from a polyester-based resin, which is characterized by having at least the following steps (1) to (2) when the main shrinkage direction is the MD direction and the direction orthogonal to the main shrinkage direction is the TD direction. It is a method for producing a polyester-based heat-shrinkable film. Step (1): A step of preparing a dicarboxylic acid compound and a diol compound as reaction components and reacting them to produce a polyester-based resin. Step (2): A step of subjecting the polyester-based resin to a stretching treatment along the MD direction to obtain a polyester-based heat-shrinkable film having the following configurations (a) to (c). (a) The 2θ value obtained by an X-ray diffraction measurement device includes a crystal peak showing a maximum value in the diffraction angle range (42° or more to less than 44°) of the (-105) plane, and the half-value width of the crystal peak is a value of 6° or less. (b) The crystallite size of the (-105) plane obtained by an X-ray diffraction measurement device is a value of 3.2 nm or less. (c) When the heat shrinkage rate under the shrinkage conditions of 80°C for 30 seconds is taken as A1, A1 is a value within the range of 15 to 60%. By stretching and manufacturing in such a manner that the MD direction becomes the main shrinkage direction, it can usually be applied to drug containers, dry batteries, tapes, etc. that are heat-shrunk after coating a polyester-based heat-shrinkable film in the gravity direction. Therefore, not only PET bottles but also when applied to the outer packaging films of various products, a polyester-based heat-shrinkable film that quantitatively suppresses the occurrence of fine wrinkles and the like can be efficiently produced.

Brief Description of the Drawings

[0017] [Figure 1] Figures 1(a) to 1(c) are diagrams illustrating the morphology of polyester heat-shrinkable films. [Figure 2] Figure 2 illustrates the relationship between the full width at half maximum (°) and the crystallite size (nm) obtained from XRD measurements of a polyester heat-shrinkable film. [Figure 3] Figure 3 is provided to illustrate the relationship between the full width at half maximum (°) and the refractive index (-) obtained from XRD measurements of a polyester heat-shrinkable film. [Figure 4] Figures 4(a) to 4(c) are provided to illustrate the relationship between the full width at half maximum (°) obtained from XRD measurements of polyester heat-shrinkable films and the heat shrinkage rates A1 (%) at 80°C and 30 seconds, A2 (%) at 70°C and 30 seconds, and A3 (%) at 100°C and 30 seconds, respectively. [Figure 5] Figure 5 illustrates the relationship between the full width at half maximum (°) obtained from XRD measurements of a polyester heat-shrinkable film and the haze value (relative value). [Figure 6] Figures 6(a) to 6(c) are provided to illustrate the relationship between the crystallite size (nm) obtained from XRD measurements of polyester heat-shrinkable films and the heat shrinkage rates A1 (%) at 80°C and 30 seconds, A2 (%) at 70°C and 30 seconds, and A3 (%) at 100°C and 30 seconds, respectively. [Figure 7] Figure 7 is provided to illustrate the relationship between crystallite size (nm) and refractive index (-) in the TD direction obtained from XRD measurements of a polyester heat-shrinkable film. [Figure 8] Figure 8 shows the relationship between the neck-in ratio of a polyester heat-shrinkable film and its wrinkle resistance when applied to a predetermined container and heat-shrinked. [Figure 9]Figure 9(a) corresponds to Example 1 and is a diagram (photograph) showing the appearance of a cylindrical label when the adherend is a PET bottle and no wrinkles have occurred. Figures 9(b) to (d) are enlarged views of the areas P, Q, and R of the appearance shown in Figure 9(a), respectively. [Modes for carrying out the invention]

[0018] [First Embodiment] The first embodiment is a polyester heat-shrinkable film 10 derived from a polyester resin, as illustrated in Figures 1(a) to (c), characterized in that it satisfies the following configurations (a) to (c) when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction. (a) The 2θ value obtained by the X-ray diffraction analyzer includes a crystal peak that shows the maximum value at the diffraction angle of the (-10⁵) plane (in the range of 42° or more to less than 44°), and the full width at half maximum of the crystal peak is 6° or less. (b) The crystallite size of the (-10⁵) plane obtained by the X-ray diffraction analyzer shall be 3.2 nm or less. (c) When the thermal shrinkage rate in the MD direction is A1 under shrinkage conditions of 80°C for 30 seconds, A1 shall be a value within the range of 15 to 60%. The following describes in detail a polyester heat-shrinkable film of the first embodiment, in which the MD direction is the primary shrinkage direction, with reference to the drawings as appropriate.

[0019] 1. Polyester resin The type of polyester resin constituting the polyester heat-shrinkable film of the first embodiment is not particularly limited, but it is preferably derived from a polyester resin composition containing an amorphous polyester resin and a crystalline polyester resin (however, this includes cases where the crystalline polyester resin is not included).

[0020] (1) Amorphous polyester resin As an amorphous polyester resin, any polymer derived from polyalcohols and dicarboxylic acids that is in an amorphous state at room temperature can be used. Therefore, it is preferable to use an amorphous polyester resin composed of a polyalcohol and a hydroxycarboxylic acid, an amorphous polyester resin composed of a polyalcohol dicarboxylic acid and a hydroxycarboxylic acid, or a mixture thereof of these polyester resins. Furthermore, whether or not a material is an amorphous polyester resin can be determined by the fact that the melting peak of the crystalline portion does not basically appear in the DSC curve obtained by DSC (Differential Scanning Calorimeter).

[0021] Here, examples of polyalcohols that are raw material components of amorphous polyester resin include at least one diol such as aliphatic diols like ethylene glycol, diethylene glycol, propanediol, butanediol, neopentyl glycol, and hexanediol, alicyclic diols like 1,4-hexanedimethanol, and aromatic diols. Therefore, among these polyalcohols, ethylene glycol, diethylene glycol, and 1,4-hexanedimethanol are particularly preferred. The reason for this is that by using such polyalcohols, it is easier to obtain amorphous polyester resins in which the amorphous properties are controlled to the desired state by reacting them appropriately with polycarboxylic acids. Furthermore, examples of dicarboxylic acids used as raw material components for amorphous polyester resins include fatty acid dicarboxylic acids such as adipic acid, sebacic acid, and azelaic acid; aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid, and isophthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; or at least one of these ester-forming derivatives. Among these, terephthalic acid is more preferable because it is stable, readily reacts with polyalcohols, and is relatively inexpensive. Furthermore, at least one of the following can be used as a hydroxycarboxylic acid compound component of polyester resin: lactic acid, hydroxybutyric acid, polycaprolactone, etc.

[0022] (2) Crystalline polyester resin On the other hand, as a crystalline polyester resin, basically any polyester resin that has a crystalline portion at room temperature can be used. Therefore, it is preferable that the material be a polyester resin composed of a polyalcohol and a dicarboxylic acid, a polyester resin composed of a polyalcohol and a hydroxycarboxylic acid, a polyester resin composed of a polyalcohol dicarboxylic acid and a hydroxycarboxylic acid, or a mixture thereof of these polyester resins. Furthermore, whether or not a material is a crystalline polyester resin can be determined by observing the DSC (Differential Scanning Calorimeter) curve obtained by a DSC, which basically shows a melting peak of the crystalline portion within a predetermined temperature range.

[0023] Here, the polyalcohols that are raw material components of crystalline polyester resins include at least one diol, such as aliphatic diols like ethylene glycol, diethylene glycol, propanediol, butanediol, neopentyl glycol, and hexanediol, alicyclic diols like 1,4-hexanedimethanol, and aromatic diols, similar to the reaction components of amorphous polyester resins. Among these, ethylene glycol, diethylene glycol, and 1,4-hexanedimethanol are more preferred because they react stably with dicarboxylic acids. Furthermore, examples of dicarboxylic acids used as raw material components for crystalline polyester resins include fatty acid dicarboxylic acids such as adipic acid, sebacic acid, and azelaic acid; aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid, and isophthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; or at least one of these ester-forming derivatives.

[0024] Therefore, examples of crystalline polyester resins include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and polypropylene terephthalate, but it may be a crystalline polyester resin alone or a mixture of multiple crystalline polyester resins. In particular, as an example of a crystalline polyester resin, a crystalline polyester resin consisting of 100 parts by weight of terephthalic acid and 100 parts by weight of ethylene glycol in terms of the total amount of reactive components can be suitably used.

[0025] (3) Mixing ratio In a polyester resin composition, it is also preferable to include a predetermined amount of amorphous polyester resin relative to the total amount of the blended components. More specifically, it is preferable to include 20 to 100% by weight of amorphous polyester resin and 0% by weight, or 0 to 80% by weight (excluding 0% by weight) of crystalline polyester resin, relative to the total amount (100% by weight). The reason for this is that by limiting the proportions of amorphous polyester resin and crystalline polyester resin during the mixing process, even with some phase separation, a uniform mixture can be achieved, making it easier to adjust viscoelastic properties such as the loss coefficient, as well as mechanical properties. Therefore, the thermal shrinkage rate and maximum shrinkage stress near the shrinkage temperature can be more easily adjusted to the desired range, and the haze value and other parameters can be controlled with greater precision and quantitative accuracy.

[0026] More specifically, when the content of amorphous polyester resin falls below 20% by weight, it becomes difficult to adjust viscoelastic properties such as the loss coefficient, which can make it difficult to control the thermal shrinkage rate, mechanical strength, or maximum shrinkage stress of the polyester heat-shrinkable film near its shrinkage temperature. Therefore, it is more preferable to include 50-90% by weight of amorphous polyester resin and 10-50% by weight of crystalline polyester resin, and even more preferable to include 70-90% by weight of amorphous polyester resin and 10-30% by weight of crystalline polyester resin, relative to the total amount.

[0027] 2.Configuration (a) The structure (a) of the polyester heat shrinkable film is characterized in that (a) the 2θ value obtained by the X-ray diffraction measuring device includes a crystal peak that shows the maximum value at the diffraction angle of the (-10⁵) plane (in the range of 42° or more to less than 44°), and the full width at half maximum of the crystal peak is 6° or less. The reason for this is that XRD measurement, a simple yet precise optical measurement method, can limit the full width at half maximum of the crystal peak corresponding to the (-10⁵) plane to a narrow value of 6° or less. Therefore, by controlling the full width at half maximum of the crystal peak, the occurrence of fine wrinkles and other defects can be suppressed accurately and quantitatively, even when applied to various containers.

[0028] Conversely, if the full width at half maximum of the crystal peak obtained using an X-ray diffraction measuring device (transmitted light) exceeds 6°, it becomes difficult to control thermal shrinkage, and it may become difficult to quantitatively suppress the occurrence of fine wrinkles, etc. However, if the full width at half maximum of the crystal peak is made excessively narrow, the manufacturing yield may decrease significantly, or the types of polyester resins that can be used may be excessively limited. Therefore, it is more preferable to limit the full width at half maximum (FWHM) of the crystal peaks obtained by XRD measurement to a value within the range of 1 to 5.5°, and even more preferable to limit it to a value within the range of 2 to 5°.

[0029] Here, we will refer to Figure 2 and explain the relationship between the full width at half maximum (°) of the crystal peak obtained by XRD measurement and the crystallite size (nm). In other words, from the characteristic curve in Figure 2, it can be seen that the crystallite size tends to decrease inversely with increasing full width at half maximum.

[0030] More specifically, the characteristic curve in Figure 2 shows that when the full width at half maximum is 3 to 6°, the crystallite size is obtained in the range of 1.5 to 3.2 nm. Furthermore, it can be understood that when the full width at half maximum (FWHM) exceeds 3°, the crystallite size decreases to a value of approximately 3.2 nm or less; when the FWHM exceeds 4°, it decreases to a value of approximately 2.5 nm or less; and when the FWHM exceeds 5°, the crystallite size decreases to a value of approximately 2 nm or less.

[0031] In fact, in the case of Example 1, which will be described later, a crystallite size of approximately 2.1 to 3.1 nm was obtained by adjusting the full width at half maximum to about 2.8 to 4.4°. Therefore, by controlling the full width at half maximum (FWHM) of the crystal peaks in the measurement chart obtained by XRD measurement to a predetermined range (6° or less), a desired crystallite size (3.2 nm or less) can be obtained, although this is also related to other influencing factors.

[0032] Next, referring to Figure 3, we will explain the relationship between the full width at half maximum (FMAX) of the crystal peak obtained by XRD measurement and the refractive index (-) in the TD direction (hereinafter sometimes simply referred to as the refractive index). In other words, judging from the characteristic curve in Figure 3, as the full width at half maximum increases from about 2.5°, the refractive index in the TD direction tends to decrease almost exponentially up to about 4-4.5°. On the other hand, when the full width at half maximum exceeds 4.5° and reaches 5-6°, there is a tendency for the refractive index in the TD direction to increase.

[0033] In fact, in the case of Example 1, which will be described later, a refractive index of approximately 1.558 to 1.572 is obtained by setting the full width at half maximum (FMAX) to approximately 2.8 to 4.4° in the TD direction. Therefore, by controlling the full width at half maximum of the crystal peaks obtained by XRD measurement to a predetermined range (for example, 3 to 6°), it is possible to obtain a desired range of refractive index values ​​in the TD direction, although this is also related to other influencing factors.

[0034] Next, we will refer to Figures 4(a) to (c) and explain the relationship between the full width at half maximum (FMAX) of the crystal peaks and the thermal shrinkage rates A1 (%) at 80°C and 30 seconds, A2 (%) at 70°C and 30 seconds, and A3 (%) at 100°C and 30 seconds. In other words, from the characteristic curves in Figures 4(a) to (c), it can be seen that, up to a full width at half maximum (FMAX) of approximately 2.5 to 4.5°, the thermal contraction rate at each temperature tends to increase with increasing FMAX. On the other hand, it can be seen that when the full width at half maximum (FMAX) exceeds approximately 4.5°, the FMAX tends to decrease as it increases.

[0035] In fact, in the case of Example 1 and others described later, a thermal shrinkage rate (A1) of approximately 17-55% was obtained by setting the half-width to approximately 2.8-4.4° for 80°C and 30 seconds. Similarly, for a thermal shrinkage coefficient A2 at 70°C for 30 seconds, values ​​of approximately 1-16% can be obtained by setting the half-width to a value of about 2.8-4.4°. Furthermore, similarly, for a heat shrinkage coefficient A3 at 100°C for 30 seconds, values ​​of approximately 29-71% were obtained by setting the half-width to around 2.8-4.4°. Therefore, by controlling the full width at half maximum of the crystal peaks obtained by XRD measurement to a predetermined range (for example, 6° or less), although this is also related to other influencing factors, the thermal shrinkage rate from 70°C to 100°C can be accurately controlled to the desired range.

[0036] Next, we will refer to Figure 5 and explain the relationship between the full width at half maximum (°) of the crystal peak obtained by XRD measurement and the haze value (%). In other words, judging from the characteristic curve in Figure 5, it can be seen that there is a direct proportional relationship, where the haze value is in the range of approximately 1.5 to 8% when the full width at half maximum is in the range of approximately 2.5 to 6°.

[0037] In fact, in the case of Example 1, which will be described later, a haze value of approximately 1.9 to 6.4% was obtained by setting the full width at half maximum to approximately 2.8 to 4.4°. Therefore, although it is related to other influencing factors, by strictly controlling the full width at half maximum obtained from XRD measurements to a predetermined range (for example, 6° or less), it is possible to effectively obtain a low haze value of 10% or less.

[0038] 3. Configuration (b) Furthermore, the polyester heat-shrinkable film configuration (b) is characterized by having a crystallite size of 3.2 nm or less for the (-10⁵) plane obtained by XRD measurement. This is because XRD measurement, a simple yet precise measurement method, can limit the crystallite size of the (-10⁵) plane to a relatively small value of 3.2 nm or less. Therefore, even when applied to various containers, the occurrence of fine wrinkles and other defects can be suppressed accurately and quantitatively.

[0039] Conversely, when the crystallite size exceeds 3.2 nm, it becomes difficult to control thermal shrinkage, making it difficult to quantitatively suppress the occurrence of fine wrinkles and other defects. However, attempting to control the crystallite size to an excessively small degree may result in a significant decrease in manufacturing yield or excessively restrict the types of polyester resins that can be used. Therefore, it is more preferable to limit the crystallite size obtained by XRD measurement to a value within the range of 0.5 to 2.3 nm, and even more preferable to limit it to a value within the range of 1.3 to 2.1 nm.

[0040] Next, referring to Figures 6(a) to (c), we will explain the relationship between the crystallite size (nm) obtained by XRD measurement and the thermal shrinkage rates A1 (%) at 80°C and 30 seconds, A2 (%) at 70°C and 30 seconds, and A3 (%) at 100°C and 30 seconds. In other words, judging from the characteristic curve in Figure 6, in the crystallite size range of 1 to 2 nm, the thermal contraction rate at 70°C to 100°C for 30 seconds each tends to increase sharply, and when the crystallite size exceeds 2 nm, the thermal contraction rate at 70°C to 100°C for 30 seconds each tends to decrease rapidly or gradually, depending on the temperature.

[0041] In fact, in the case of Example 1 and others described later, a thermal shrinkage rate of approximately 17-55% was obtained for a thermal shrinkage rate A1 at 80°C for 30 seconds by setting the crystallite size to approximately 1.5-3.2 nm. Similarly, for thermal shrinkage A2 at 70°C for 30 seconds, a thermal shrinkage range of approximately 1-16% was obtained by setting the crystallite size to about 1.5-3.2 nm. Furthermore, for the thermal shrinkage coefficient A3 at 100°C for 30 seconds, values ​​in the range of approximately 29-71% were obtained by setting the crystallite size to approximately 1.5-3.2 nm. Therefore, by strictly limiting the crystallite size obtained by XRD measurement to a predetermined range (for example, 3.2 nm or less), the thermal shrinkage values ​​at 70°C to 100°C for 30 seconds each can be limited to a desired range.

[0042] 4. Composition (c) The polyester heat-shrinkable film (c) is characterized in that, when the heat shrinkage rate when heat-shrinking in the MD direction under shrinkage conditions of 80°C and 30 seconds is defined as A1, the value of A1 is within the range of 15 to 60%. The reason for this is that, under these thermal shrinkage temperature conditions, the crystallite size and other parameters obtained by XRD measurement can be controlled, and by controlling the desired thermal shrinkage rate at a common temperature of 80°C, the occurrence of fine wrinkles and other issues can be quantitatively suppressed. However, if the heat shrinkage coefficient A1 in the MD direction falls below 15% or, conversely, exceeds 60%, the manufacturing yield may decrease significantly, or the types of polyester resins that can be used may be excessively limited. Therefore, it is more preferable to limit the thermal shrinkage coefficient A1 in the MD direction to a value within the range of 35 to 55%, and even more preferable to limit it to a value within the range of 38 to 50%. Furthermore, the thermal shrinkage rate in the TD direction of the polyester heat-shrinkable film is preferably in the range of -10 to 10% under shrinkage conditions of 80°C for 30 seconds, and more preferably in the range of -5 to 5%.

[0043] 5.Configuration (d) The polyester heat-shrinkable film is characterized by having a refractive index in the TD direction within the range of 1.55 to 1.60, as defined in configuration (d). The reason for this is that by using a simple yet precise measurement method such as a refractometer, the refractive index in the TD direction can be limited to a relatively narrow range, thereby suppressing the occurrence of fine wrinkles and other defects with high accuracy and quantitative precision, even when applied to various containers. Conversely, if the refractive index falls below 1.55 or exceeds 1.60, it becomes difficult to control thermal shrinkage, making it challenging to quantitatively suppress the occurrence of fine wrinkles and other issues.

[0044] Therefore, it is more preferable to limit the refractive index to a value within the range of 1.555 to 1.595, and even more preferable to limit it to a value within the range of 1.56 to 1.59. Furthermore, as will be described later in Example 1, etc., such refractive index can be measured using a refractometer in accordance with JIS K7142:2014.

[0045] 6. Configuration (e) As for the composition (e) of the polyester heat-shrinkable film, it is preferable that the heat shrinkage rate when heat-shrinking in the MD direction under shrinkage conditions of 70°C and 30 seconds is A2, and that A2 is a value within the range of 1 to 35%. The reason for this is that by limiting the thermal shrinkage rate at 70°C for 30 seconds, it becomes easier to obtain an appropriate thermal shrinkage rate even at relatively low temperatures to suit various applications, and consequently, to obtain the desired maximum shrinkage stress. Therefore, it is more preferable that the thermal shrinkage rate in the MD direction at 70°C for 30 seconds be within the range of 3 to 20%, and even more preferable that it be within the range of 5 to 15%. Furthermore, the thermal shrinkage rate in the TD direction of the polyester heat-shrinkable film is preferably in the range of -7 to 7% under shrinkage conditions of 70°C for 30 seconds, and more preferably in the range of -3 to 3%.

[0046] 7.Configuration (f) As for the composition (f) of the polyester heat-shrinkable film, it is preferable that the heat shrinkage rate when heat-shrinking in the MD direction under shrinkage conditions of 100°C for 30 seconds is A3, and that A3 is within the range of 30 to 80%. The reason for this is that by limiting the thermal shrinkage rate at 100°C, a good thermal shrinkage rate can be obtained in polyester-based heat-shrinkable films during thermal shrinkage, and consequently, the maximum shrinkage stress can be more easily obtained. Therefore, it is more preferable to set the 100°C heat shrinkage rate in the MD direction to a value within the range of 40 to 75%, and even more preferable to set it to a value within the range of 45 to 73%. Furthermore, the thermal shrinkage rate in the TD direction of the polyester heat-shrinkable film is preferably in the range of -10 to 10% under shrinkage conditions of 100°C for 30 seconds, and more preferably in the range of -5 to 5%.

[0047] 8. Composition (g) As a component (g), it is preferable that the haze value of the heat-shrinkable film (film thickness: usually 25-50 μm), measured in accordance with JIS K 7136:2000, be 10% or less. The reason for this is that by controlling the haze value of the heat-shrinkable film within a predetermined range, not only is its transparency improved, but its printability and uniform heat shrinkage can also be further enhanced. However, if the haze value is made excessively small, the types and amounts of polymer components that can be used may be limited, making it difficult to control during manufacturing and potentially leading to an excessive decrease in production efficiency. Therefore, it is more preferable to set such haze value to a value within the range of 1 to 8%, and even more preferable to set it to a value within the range of 2 to 6%.

[0048] 9.Configuration (h) In configuration (h), it is preferable that the neck-in ratio, measured under the condition of being in 70°C hot water for 10 seconds, be 4% or less. The reason for this is that, by considering the neck-in phenomenon that normally occurs during film production and limiting the neck-in rate, which mimics this phenomenon, to a predetermined range, excellent wrinkle resistance can be achieved even when applied to various containers. However, if the neck-in rate becomes excessively small, it may lead to limitations on manufacturing yield and the types of raw materials that can be used, resulting in economic disadvantages. Therefore, it is more preferable to set the neck-in ratio to a value within the range of 0.01 to 2%, and even more preferable to set it to a value within the range of 0.1 to 1%. The method for measuring the neck-in ratio will be described in detail in Example 1 and other sections below. For reference, Figure 8 shows the relationship between the neck-in ratio of a polyester heat-shrinkable film and its wrinkle resistance when applied to a specified container and heat-shrinked (5 points: neck-in ratio of 0-1%, 3 points: neck-in ratio greater than 1-2%, 1 point: neck-in ratio greater than 2-4%, 0 points: neck-in ratio greater than 4%).

[0049] 10. Thickness The thickness of the polyester heat-shrinkable film is usually preferably within the range of 10 to 100 μm. The reason for this is that by specifically limiting the film thickness before heat shrinkage to a predetermined range, it becomes easier to manufacture a uniform thickness, and it also becomes easier to control the heat shrinkage rate and the maximum shrinkage stress, thereby making it easier to prevent uneven shrinkage. Therefore, it is more preferable to set the film thickness before heat shrinkage to a value in the range of 20 to 60 μm, and even more preferable to set it to a value in the range of 30 to 50 μm.

[0050] 11. Composition of polyester heat-shrinkable film It is preferable to incorporate various additives into the polyester heat-shrinkable film, or to attach them to one or both sides thereof. More specifically, it is preferable to blend at least one of the following—hydrolysis inhibitors, antistatic agents, ultraviolet absorbers, infrared absorbers, colorants, organic fillers, inorganic fillers, organic fibers, inorganic fibers, etc.—in an amount of typically 0.01 to 10% by weight relative to the total amount of the polyester heat shrink film, and more preferably in an amount of 0.1 to 1% by weight.

[0051] Furthermore, as shown in Figure 1(b), it is also preferable to laminate other resin layers 10a, 10b containing at least one of these various additives onto one or both sides of the polyester heat-shrinkable film 10. In that case, when the thickness of the polyester heat-shrinkable film is set to 100%, it is preferable that the single-layer thickness or total thickness of the additionally laminated resin layers be within the range of 0.1 to 10%.

[0052] Furthermore, the resin that constitutes the other resin layers may be a polyester resin similar to that used in polyester heat-shrinkable films, or it is preferable that it be at least one of the following: an acrylic resin, an olefin resin, a urethane resin, a rubber resin, etc.

[0053] Furthermore, it is preferable to provide a multilayer structure for the polyester heat shrink film to further enhance hydrolysis prevention and mechanical protection, or to provide a shrinkage rate adjustment layer 10c on the surface of the polyester heat shrink film 10, as shown in Figure 1(c), so that the shrinkage rate of the polyester heat shrink film becomes uniform across the surface. Such shrinkage rate adjustment layers can be laminated using adhesives, coating methods, or heat treatment, depending on the shrinkage characteristics of the polyester heat-shrinkable film.

[0054] More specifically, the thickness of the shrinkage rate adjustment layer is in the range of 0.1 to 3 μm, and it is preferable to laminate a shrinkage rate adjustment layer of a type that suppresses the shrinkage rate of the polyester heat shrink film at a predetermined temperature if the shrinkage rate is excessively large. Furthermore, if the shrinkage rate of the polyester heat-shrinkable film at a predetermined temperature is excessively small, it is preferable to laminate a shrinkage rate adjustment layer that expands the shrinkage rate. Therefore, as a polyester heat-shrinkable film, the aim is to obtain the desired shrinkage rate by using a shrinkage rate adjustment layer, without having to create various heat-shrinkable films with different shrinkage rates.

[0055] [Second Embodiment] The second embodiment is a method for manufacturing a polyester heat-shrinkable film 10 derived from a polyester resin, as illustrated in Figure 1(a), and is characterized by having at least the following steps (1) to (2), when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction. Step (1): A step to prepare a dicarboxylic acid compound and a diol compound as reaction components and react them to produce a polyester resin. Step (2): A step to obtain a polyester heat-shrinkable film having the following configurations (a) to (c) by stretching a polyester resin along the MD direction. (a) The 2θ value obtained by the X-ray diffraction analyzer includes a crystal peak that shows the maximum value at the diffraction angle of the (-10⁵) plane (in the range of 42° or more to less than 44°), and the full width at half maximum of the crystal peak is 6° or less. (b) The crystallite size of the (-10⁵) plane obtained by the X-ray diffraction analyzer shall be 3.2 nm or less. (c) When shrinkage is performed under the conditions of 80°C for 30 seconds, the thermal shrinkage rate is A1, and A1 is set to a value within the range of 15 to 60%. The method for manufacturing a polyester heat-shrinkable film obtained by longitudinally stretching along the MD direction using a longitudinal stretching apparatus, according to the second embodiment, will be described in detail below with reference to the drawings as appropriate.

[0056] 1. Preparation and mixing of raw materials First, it is preferable to prepare main components and additives such as crystalline polyester resin, amorphous polyester resin, rubber-based resin, antistatic agents, and hydrolysis inhibitors as raw materials. Next, it is preferable to weigh the prepared crystalline polyester resin, amorphous polyester resin, etc., into the stirring container in a predetermined mixing ratio, and then mix them using a stirring device until they become uniform.

[0057] 2. Process for creating the raw material sheet Next, it is preferable to heat the uniformly mixed raw materials to a predetermined temperature and dry them until they are completely dry, in order to eliminate the effects of moisture and other factors. Next, it is preferable to typically perform extrusion molding to create a raw material sheet of a predetermined thickness. More specifically, for example, using an extruder (manufactured by Tanabe Plastic Machinery Co., Ltd.) with an L / D ratio of 24 and an extrusion screw diameter of 50 mm, under conditions of an extrusion temperature of 230 to 270°C, extrusion molding can be performed to obtain a raw material sheet of a predetermined thickness (usually 30 to 1000 μm).

[0058] 3. Preparation of polyester heat-shrinkable film Next, the obtained raw sheet is stretched primarily in the MD direction using a longitudinal stretching device, while moving it on and between rolls, to produce a polyester heat-shrinkable film. In other words, it is preferable to use a predetermined longitudinal stretching device and stretch the film in the MD direction while heating and pressing, while basically increasing the film width at a preheating temperature, stretching temperature, heat setting temperature, and stretching ratio described later, thereby crystallizing the polyester molecules constituting the polyester heat shrinkable film into a predetermined shape.

[0059] Here, any known longitudinal stretching device can be used as appropriate, but it is preferable to use a longitudinal stretching device in which multiple roll groups are arranged continuously in a predetermined direction (such as the horizontal direction). Then, for example, it is preferable to preheat the film on a preheating roll until the film temperature reaches a predetermined temperature (for example, around 70°C), and then stretch the film between stretching rolls, where the surface temperature is set to, for example, 95°C, to typically 2 to 5 times its initial thickness. Next, by solidifying the film using a cooling roll, a heat-shrinkable polyester-based heat-shrinkable film can be obtained.

[0060] On the other hand, it is also preferable to perform a lateral stretching process using a tenter before performing the longitudinal stretching process using a longitudinal stretching device. In other words, it is also preferable to preheat the unstretched film until the film temperature reaches 90°C, then stretch it transversely in a tenter to four times its original size, for example at 75°C, and then heat-set it. Next, it is preferable to further stretch the obtained stretched film using a longitudinal stretching device.

[0061] Furthermore, it is also preferable to further stretch the film that has been stretched longitudinally using a longitudinal stretching device in the transverse direction using a tenter to obtain a heat-shrinkable polyester film. In other words, after performing a stretching process using a longitudinal stretching device, it is also preferable to further stretch the obtained film transversely using a tenter while heat-treating it at a predetermined temperature (for example, 100°C) for about 1 to 5 seconds to obtain a predetermined heat-shrinkable polyester film.

[0062] 4. Inspection Process Next, it is preferable to include an inspection step to confirm whether or not the product is a polyester heat-shrinkable film having one of the configurations (a) to (c). In other words, by creating a predetermined polyester heat-shrinkable film as the object to be measured, and using XRD to inspect and confirm that the full width at half maximum of the crystal peaks, the crystallite size, and the heat shrinkage rate under predetermined shrinkage conditions are within a predetermined range, it is possible to suppress the occurrence of fine wrinkles and other issues even when applied to various containers, etc.

[0063] Furthermore, since the components (a) and (b) can be inspected using XRD, it is possible to measure and control them in-line during the manufacturing process of polyester heat-shrinkable films. At that time, it is also preferable to confirm that the thickness of the polyester heat-shrinkable film is within a predetermined range.

[0064] 5. Others The obtained polyester heat-shrinkable film is immersed in hot water under predetermined conditions of temperature and duration using a predetermined heating device, or subjected to heat treatment to cause the polyester heat-shrinkable film to shrink, and the heat shrinkage rate is measured. Furthermore, it is preferable to measure the haze, glass transition temperature, and various thermal properties of the polyester heat-shrinkable film and check that they are within a predetermined range. Then, it is preferable to attach the obtained polyester heat-shrinkable film to an object such as a container, heat-treat it under predetermined conditions, and evaluate the uniform shrinkage properties of the polyester heat-shrinkable film.

[0065] Furthermore, it is preferable to include an inspection process to continuously or intermittently measure the following characteristics of the created polyester heat-shrinkable film and confirm that they are within a predetermined range. In other words, by measuring the following characteristics through the prescribed inspection process and confirming that they fall within a predetermined range, quality control can be performed accurately and quantitatively, even if there are some variations in shrinkage conditions. 1) Visual inspection of the appearance of polyester heat shrinkable film 2) Measurement of thickness variation 3) Haze measurement 4) Measurement of the glass transition temperature 5) Measurement of melting point and heat of fusion 6) Measurement of tensile modulus 7) Measurement of tear strength 8) SS curve measurement

[0066] [Third Embodiment] The third embodiment is an embodiment of the first embodiment concerning the method of using a polyester heat-shrinkable film that is longitudinally stretched along the MD direction. In other words, any known method of using heat-shrinkable film can be suitably applied. For example, when implementing a method for using polyester heat-shrinkable film, first, the polyester heat-shrinkable film is cut to an appropriate length and width, and a long cylindrical object is formed. Next, the long cylindrical object is supplied to an automatic labeling device (shrink labeler), cut to the required length, and then fitted onto a predetermined container filled with its contents.

[0067] Next, the polyester heat-shrinkable film fitted onto a predetermined container is subjected to a heat treatment by passing it through a hot air tunnel or steam tunnel at a predetermined temperature. Then, by using radiant heat such as infrared rays provided in these tunnels, and by blowing heated steam at around 80°C from the surroundings, the polyester heat-shrinkable film is uniformly heated and thermally shrunk. Therefore, a polyester heat-shrinkable film of a predetermined configuration can be adhered to the outer surface of a predetermined container or the like, allowing for the rapid production of a labeled container. On the other hand, when a polyester heat-shrinkable film of a predetermined configuration is used, areas are created from the top to the bottom of the bottle body where the label does not conform to the perimeter of the container, and wrinkles are also observed to be significantly present. [Examples]

[0068] The present invention will be described in detail below based on examples. However, the scope of the present invention will not be narrowed by the description of the examples without any particular reason. The polyester resins used in Example 1 and other examples are as follows:

[0069] (PETG1) A non-crystalline polyester resin consisting of dicarboxylic acid: 100 mol% terephthalic acid, diols: 63 mol% ethylene glycol, 24 mol% 1,4-cyclohexanedimethanol, and 13 mol% diethylene glycol (glass transition temperature: 69°C). (PETG2) A non-crystalline polyester resin consisting of dicarboxylic acid: 100 mol% terephthalic acid, diol: 67 mol% ethylene glycol, and 33 mol% 1,4-cyclohexanedimethanol (glass transition temperature: 68°C). (APET) A crystalline polyester composed of 100 mol% dicarboxylic acid (terephthalic acid) and 100 mol% diol (ethylene glycol) (exhibiting a predetermined melting point, but with a glass transition temperature of 80°C and an intrinsic viscosity of 0.65 dL / g).

[0070] [Example 1] 1. Preparation of polyester heat-shrinkable film In a stirring container, amorphous polyester resin (PETG1) was placed in a ratio of 70 parts by weight, crystalline polyester resin (APET) in a ratio of 30 parts by weight, and additives in a ratio of 0.8 parts by weight, relative to the total volume. The mixture was then uniformly mixed and stirred to obtain the raw material for polyester heat-shrinkable film. Next, after the raw materials were completely dried, they were extruded at an extrusion temperature of 260°C using an extruder (manufactured by Tanabe Plastic Machinery Co., Ltd.) with an L / D ratio of 24 and an extrusion screw diameter of 50 mm to obtain a raw sheet.

[0071] Next, using a heat-shrinkable film manufacturing apparatus, a polyester heat-shrinkable film with a thickness of 45 μm was prepared by longitudinal stretching the raw sheet at a preheating temperature of 84°C, a stretching temperature of 84°C, a stretching ratio (MD direction: 400%, TD direction: 100%), and a heat-fixing temperature of 75°C.

[0072] 2. Evaluation of polyester heat-shrinkable films (1) Rating 1: Half width Using an X-ray diffraction analyzer (Rigaku Corporation, RINT-RAPID, transmission method), the full width at half maximum (FWHM) of the crystal peak whose 2θ value was maximum at the diffraction angle of the (-10⁵) plane (in the range of 42° to less than 44°) was measured. The results are shown in Table 2.

[0073] (2) Rating 2: Crystallite size The crystallite size of the (-10⁵) plane was measured using the above-described X-ray diffraction apparatus. The results are shown in Table 2.

[0074] (3) Evaluation 3: Thermal shrinkage rate (A1) The thermal shrinkage rate A1 was measured when the material was heat-shrinkage in the MD direction under shrinkage conditions of 80°C for 30 seconds, and the thermal shrinkage rate (A1) was calculated according to the following formula. The results are shown in Table 2. Heat shrinkage rate = (Length of film before heat shrinkage - Length of film after heat shrinkage) / Length of film before heat shrinkage × 100

[0075] (4) Rating 4: Refractive index The refractive index in the TD direction was measured using a refractometer in accordance with JIS K7142:2014. The results are shown in Table 2.

[0076] (5) Rating 5: Thermal shrinkage rate (A2) In Evaluation 5, the thermal shrinkage rate (A2) of the polyester heat-shrinkable film in the MD direction was measured in the same manner as in Evaluation 3, except that the thermal shrinkage conditions were changed from 80°C and 30 seconds to 70°C and 30 seconds. The results obtained are shown in Table 2.

[0077] (6) Evaluation 6: Thermal shrinkage rate (A3) In Evaluation 6, the thermal shrinkage rate (A3) of the polyester heat-shrinkable film in the MD direction was measured in the same manner as in Evaluation 3, except that the shrinkage conditions were changed from 80°C and 30 seconds to 100°C and 30 seconds. The results obtained are shown in Table 2.

[0078] (7) Rating 7: Haze value The haze value of the obtained polyester heat-shrinkable film (thickness 45 μm) was measured in accordance with JIS K 7136:2000. The results are shown in Table 2.

[0079] (8) Rating 8: Neck-in rate The obtained polyester heat-shrinkable film was measured for neck-in ratio under the condition of being immersed in 70°C hot water for 10 seconds, with the main shrinkage direction (MD direction) fixed, and evaluated according to the following criteria. Specifically, a polyester heat-shrinkable film was cut into a long strip with dimensions of 200 mm or more in the main shrinkage direction and 100 mm in the perpendicular direction, and used as the measurement sample. A mark was drawn in advance at the center of the main shrinkage direction in the measurement sample, perpendicular to the main shrinkage direction, and the length of this mark was defined as L0.

[0080] Next, the measurement sample was fixed to a fixed frame jig with an internal length of 140 mm and a width of 140 mm, with the main shrinkage direction aligned with the internal length direction, so that both ends of the measurement sample were fixed to the fixed frame jig. On the other hand, the elongated measurement sample was positioned and fixed so that a predetermined space was created between both sides of the elongated measurement sample in the orthogonal direction and the fixed frame jig.

[0081] Next, the measurement sample, mounted on a fixed frame jig, was immersed in 70°C hot water for 10 seconds, and then in water below 30°C for 10 seconds. The maximum thermal shrinkage rate in the orthogonal direction was measured from the change in the length of the gauge line on the measurement sample. Finally, the obtained thermal shrinkage rate was divided by 2 according to the following formula (1) and measured as the neck-in rate.

[0082]

number

[0083] Furthermore, it has been found that the best finish is achieved when the neck-in rate is within the range of 0-2%, even when applied to containers with complex shapes (such as medicine containers, batteries, and tape). Furthermore, if the neck-in rate is within the range of 2% to 4%, the finish after application may be slightly reduced when applied to containers with complex shapes, but the overall finish is generally good. Furthermore, if the neck-in rate is within the range of 4% to 6%, the finish after application will be further reduced when applied to containers with complex shapes, but the finish is still practically acceptable. However, when the neck-in ratio exceeds 6, the finished product after installation deteriorates significantly, reaching a level that is practically unacceptable.

[0084] (9) Rating 9: Wrinkle resistance In Evaluation 9, the wrinkle resistance (sometimes referred to as adhesion evaluation) of the polyester heat-shrinkable film after heat shrinkage was measured and evaluated according to the following criteria. In other words, prepare a PET bottle container (volume: 500ml) filled with commercially available drinking water. Next, a polyester heat-shrinkable film was slit into 26 cm wide strips to obtain a long heat-shrinkable film. Perforations 1 mm wide were made along the longitudinal direction of the strip, and 1,3-dioxolane was applied to the edges in the width direction. Next, the ends in the width direction were overlapped and glued together so that there was an overlap of approximately 1 cm, creating a cylindrical label with a diameter of approximately 8 cm. Furthermore, this cylindrical label was cut into 16 cm intervals along its length to obtain multiple cylindrical labels. Next, the cylindrical label was placed over the entire PET bottle container and moved through a steam tunnel maintained at 85°C on a conveyor belt at a speed of 6 m / min, causing the cylindrical label to heat-shrink so that it adhered tightly to the entire surface of the PET bottle container from top to bottom. Next, the tubular labels after heat shrinkage were visually inspected, and their wrinkle resistance was evaluated according to the following criteria, checking for wrinkles of a specified length (1 cm or more) or width (1 mm or more). The results are shown in Table 2. ◎: Of the five cylindrical labels, none of them showed the expected wrinkle formation. ○: Of the five cylindrical labels, the specified wrinkles were not observed in three or more. △: Of the five cylindrical labels, the specified wrinkles were not observed in one or more. ×: The predetermined wrinkles were observed in all 5 of the tubular labels.

[0085] [Examples 2-5] In Examples 2 to 5, as shown in Table 1, various polyester heat-shrinkable films were prepared by varying the type and amount of polyester resin used, the manufacturing conditions, etc., and mainly stretching in the MD direction, similar to Example 1. The full width at half maximum of the crystal peaks, crystallite size, and heat shrinkage rate (A1 to A3) were measured, similar to Example 1. The results are shown in Tables 1 and 2.

[0086] [Comparative Examples 1-2] In Comparative Examples 1 and 2, a transverse stretching apparatus was used to create polyester heat-shrinkable films by changing the type of polyester resin and manufacturing conditions, as shown in Table 1, and by stretching mainly in the TD direction, unlike in Example 1. The full width at half maximum of the crystal peaks, crystallite size, and thermal shrinkage rate (A1-A3) were then measured.

[0087] [Table 1]

[0088] [Table 2] Rating 1: Half-width Rating 2: Crystallite size Evaluation 3: MD direction thermal shrinkage rate at 80°C, etc. (A1) Evaluation 4: Refractive index in the TD direction Evaluation 5: MD direction thermal shrinkage coefficient at 70°C, etc. (A2) Evaluation 6: MD direction thermal shrinkage rate at 100℃ etc. (A3) Rating 7: Haze value Rating 8: Neck-in rate Rating 9: Wrinkle resistance [Industrial applicability]

[0089] According to the present invention, in a polyester heat-shrinkable film that is mainly stretched longitudinally along the MD direction and whose main shrinkage direction is the MD direction, by measuring the full width at half maximum of the crystal peaks obtained using XRD, the crystallite size, and the heat shrinkage rate, etc., and controlling each of them within a predetermined range, it has become possible to apply this to various products such as pharmaceutical containers, dry cell batteries, tapes, and more, in addition to PET bottles. In other words, by controlling the full width at half maximum of the crystal peaks obtained using XRD, it has become possible to efficiently and accurately manage thermal shrinkage characteristics and wrinkle resistance characteristics, even when adapted to various containers. Therefore, the polyester heat-shrinkable film of the present invention can be applied to a wide range of containers and the like, significantly expanding its versatility, and its industrial applicability is extremely high. [Explanation of symbols]

[0090] 10: Polyester heat shrink film 10a: Other resin layer 1 10b: Other resin layer 2 10c: Shrinkage rate adjustment layer

Claims

1. A polyester heat-shrinkable film derived from a polyester resin, characterized in that when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction, the following configurations (a) to (c) are satisfied. (a) The 2θ value obtained by the X-ray diffraction measuring device includes a crystal peak (including crystalline domains; the same applies hereinafter) that shows the maximum value at the diffraction angle of the (-105) plane (in the range of 42° or more to less than 44°), and the full width at half maximum of the crystal peak is 6° or less. (b) The crystallite size of the (-10⁵) plane obtained by the X-ray diffraction analyzer shall be 3.2 nm or less. (c) When the thermal shrinkage rate is A1 when the material is heat-shrunk in the MD direction under shrinkage conditions of 80°C for 30 seconds, A1 shall be a value within the range of 15 to 60%.

2. The polyester heat-shrinkable film according to claim 1, characterized in that it satisfies the following configuration (d). (d) The refractive index in the TD direction shall be within the range of 1.55 to 1.

60.

3. A polyester heat-shrinkable film according to claim 1 or 2, characterized in that it satisfies the following configuration (e). (e) When the thermal shrinkage rate is A2 when the material is heat-shrunk in the MD direction under shrinkage conditions of 70°C for 30 seconds, A2 shall be a value within the range of 1 to 35%.

4. A polyester heat-shrinkable film according to claim 1 or 2, characterized in that it satisfies the following configuration (f). (f) When the thermal shrinkage rate is A3 when the material is heat-shrunk in the MD direction under shrinkage conditions of 100°C for 30 seconds, the value of A3 shall be within the range of 25 to 80%.

5. A polyester heat-shrinkable film according to claim 1 or 2, characterized in that it satisfies the following configuration (g). (g) The haze value measured in accordance with JIS K 7136:2000 shall be 10% or less.

6. A polyester heat-shrinkable film according to claim 1 or 2, characterized in that it satisfies the following configuration (h). (h) The polyester heat shrinkable film according to claim 1 or 2, characterized in that the neck-in ratio measured under the condition of being in 70°C hot water for 10 seconds is 4% or less.

7. The polyester heat-shrinkable film according to claim 1 or 2, characterized in that the thickness is within the range of 10 to 100 μm.

8. A method for producing a polyester heat-shrinkable film derived from a polyester resin, characterized in that, when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction, the method comprises at least the following steps (1) to (2). Step (1): A step to prepare a dicarboxylic acid compound and a diol compound as reaction components and react them to produce a polyester resin. Step (2): A step of stretching a polyester resin mainly along the MD direction to obtain a polyester heat-shrinkable film having the following configurations (a) to (c). (a) The 2θ value obtained by the X-ray diffraction measuring device includes a crystal peak that shows the maximum value at the diffraction angle of the (-105) plane (in the range of 42° or more to less than 44°), and the full width at half maximum of the crystal peak is 6° or less. (b) The crystallite size of the (-10⁵) plane obtained by the X-ray diffraction analyzer shall be 3.2 nm or less. (c) When shrinkage is performed under shrinkage conditions of 80°C for 30 seconds, the thermal shrinkage rate is A1, and A1 is set to a value within the range of 15 to 60%.

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