Polyester-based heat shrink film and its manufacturing method

Abstract

This invention provides a polyester-based heat-shrinkable film with excellent wrinkle-resistant properties. The polyester-based heat-shrinkable film, etc., is characterized by satisfying the following configurations (a) to (d) when the main shrinkage direction is set as the TD direction and the direction orthogonal to the main shrinkage direction is set as the MD direction: (a) It includes a crystal peak that shows a maximum value at a diffraction angle (between 42° and less than 44°) in the (-105) plane obtained by X-ray diffraction measurement apparatus, and the half-width of the crystal peak is 7° or less; (b) The crystal size in the (-105) plane obtained by X-ray diffraction measurement apparatus is 2.5 nm or less; (c) The heat shrinkage rate A1 in the TD direction is in the range of 25% to 65% under the condition of being in warm water at 80°C for 10 seconds; (d) The refractive index in the TD direction is in the range of 1.58 to 1.66.

Description

Technical Field

[0001] This invention relates to a polyester heat shrink film and a method for manufacturing the polyester heat shrink film. More specifically, this relates to polyester-based heat-shrinkable films (hereinafter, sometimes simply referred to as heat-shrinkable films) that exhibit excellent wrinkle resistance and control of the full width at half maximum (FWHM) of crystallization peaks using an X-ray diffraction apparatus (hereinafter, sometimes referred to as XRD), and their efficient manufacturing methods. Prior Technology

[0002] In the past, heat shrink film was widely used as a substrate film for labeling PET bottles, etc., and it is composed of various materials, mainly polyester resin. These heat-shrink films are heat-shrinked through channels that generate hot air or steam and then installed on containers. However, uneven shrinkage can occur during heat shrinkage, which may result in wrinkles or uneven coloring. Therefore, various heat shrink films have been proposed to prevent wrinkles or uneven coloring caused by uneven shrinkage during heat shrinkage.

[0003] For example, a polyester-based heat-shrinkable film has been proposed, which has a high heat shrinkage rate in the width direction, a small heat shrinkage rate in the long side direction, high mechanical strength in the long side direction, good perforation openness, and excellent shrinkage treatment properties (see Patent Document 1). More specifically, it is a polyester-based heat-shrinkable film, characterized by being composed of polyester resin, wherein the proportion of acid components other than terephthalic acid (A mol%) and the proportion of alcohol components other than ethylene glycol (B mol%) in all acid components of the polyester resin are in the range of 5 mol% ≤ A + B ≤ 40 mol%. Furthermore, all acidic components contain naphthalene dicarboxylic acid at a rate of 1-30 mol% and alkali metal salts of sulfophthalic acid at a rate of 0.3-3 mol%.

[0004] In addition, a polyester heat shrink film was proposed that strictly controls the amount of amorphous components in all polyester resin components, while limiting the hot water heat shrinkage rate at 80°C and 90°C in the long side direction of the film and the hot water heat shrinkage rate at 90°C in the width direction of the film (see Patent Document 2). More specifically, the film uses polyethylene terephthalate as the main component and contains one or more monomeric components that can be amorphous components in all polyester resin components, totaling more than 15 moles. Furthermore, the heat-shrinkable polyester film is characterized in that, at a processing temperature of 80°C and a processing time of 10 seconds, the hot water shrinkage rate of the polyester heat-shrinkable film is more than 30% in the long side direction of the film, more than 40% in the processing temperature of 90°C and a processing time of 10 seconds, and the hot water shrinkage rate in the width direction of the film is less than 10% in the processing temperature of 90°C and a processing time of 10 seconds.

[0005] Previous technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 08-027259 (Scope of Application, etc.) Patent Document 2: Japanese Patent Application Publication No. 2007-016120 (Scope of Application, etc.) Summary of the Invention

[0006] (a) Technical problems to be solved However, although the heat-shrinkable films described in Patent Documents 1 and 2 all limit the heat shrinkage rate within a specified range for a specified temperature and a specified shrinkage direction, they do not consider controlling the half-peak width of the crystallization peak at all. Therefore, in cases where the bottle diameter is inconsistent and the horizontal cross-sectional shape of the bottle body is complex and not circular, such as in PET bottles, heat shrinkage is prone to become uneven, making it extremely difficult to suppress the formation of fine wrinkles.

[0007] Therefore, the inventors of this application discovered that in measurements based on X-ray diffraction measuring devices (transmitted light), by limiting the half-peak width or crystal size of the crystal peak corresponding to the (-105) plane to a value within a specified range, even when applied to various PET bottles, the generation of fine wrinkles can be quantitatively suppressed, thus completing the present invention. That is, the object of the present invention is to provide a polyester heat shrink film that exhibits excellent anti-wrinkle properties with good accuracy in simple and precise measurements, even when applied to various PET bottles, and an effective method for manufacturing such a polyester heat shrink film.

[0008] (II) Technical Solution According to the present invention, a polyester heat shrink film is provided to solve the above-mentioned technical problems. The polyester heat shrink film is a polyester heat shrink film derived from a polyester resin. The film is characterized in that when the main shrinkage direction is set as the TD direction and the direction orthogonal to the main shrinkage direction is set as the MD direction, the following configurations (a) to (c) are satisfied. (a) A crystallographic peak (including the crystal domain, hereinafter the same) whose 2θ value obtained using an X-ray diffraction apparatus (usually a transmission X-ray diffraction apparatus, the same applies below) shows its maximum value at a diffraction angle (above 42° to below 44°) in the (-105) plane, and whose full width at half maximum (FWHM) is less than 7°. (b) The crystal size of the (-105) plane obtained by X-ray diffraction is less than 2.5 nm. (c) When the heat shrinkage rate during heat shrinkage in warm water at 80°C for 10 seconds along the TD direction is set as A1, A1 is a value in the range of 25% to 65%. That is, by using XRD as a simple and precise measurement method, the full width at half maximum (FWHM) of the crystallization peak and the crystal size can be controlled with good accuracy, and by satisfying the configurations (a) to (c), the generation of fine wrinkles can be quantitatively and effectively suppressed even when applied to various PET bottles.

[0009] When constituting the polyester-based heat-shrinkable film of the present invention, it is preferable to satisfy the following configuration (d). (d) The refractive index in the range of 1.58 to 1.66 in the main contraction direction (usually the TD direction). By controlling the refractive index in this way, the half-peak width of the crystallization peak or the crystal size can be controlled more precisely and effectively. This allows for the quantitative and precise suppression of fine wrinkles, even when applied to various PET bottles.

[0010] When constituting the polyester-based heat-shrinkable film of the present invention, it is preferable to satisfy the following configuration (e). (e) The heat shrinkage rate during heat shrinkage in the TD direction at 70°C for 10 seconds is set as A2, which is a value in the range of 3 to 40%. By limiting the heat shrinkage rate A2 in this way, even at widely applicable heat shrinkage temperatures such as those used in various PET bottles, the generation of fine wrinkles can be further suppressed with high precision.

[0011] When constituting the polyester-based heat-shrinkable film of the present invention, it is preferable to satisfy the following configuration (f). (f) When the heat shrinkage rate during heat shrinkage along the TD direction in warm water at 100°C for 10 seconds is set as A3, A3 is a value in the range of 30% to 80%. By limiting the heat shrinkage rate A3 in this way, even at widely applicable heat shrinkage temperatures such as those used in various PET bottles, the generation of fine wrinkles can be further suppressed with high precision.

[0012] When constituting the polyester-based heat-shrinkable film of the present invention, it is preferable to satisfy the following configuration (g). (g) The haze value measured according to JIS K 7136:2000 is less than 10%. By controlling the haze value within the specified range in this way, not only is the transparency excellent, but it also exhibits excellent printability or uniform heat shrinkage.

[0013] When constructing the polyester heat-shrinkable film of the present invention, the thickness is preferably in the range of 10 to 100 μm. By limiting the thickness in this way, it is easy to handle or manage in manufacturing, and even when applied to various PET bottles and other applications where heat shrinkage temperature varies, it is possible to suppress the formation of fine wrinkles.

[0014] Another aspect of the present invention is a method for manufacturing a polyester heat shrink film, which is a method for manufacturing a polyester heat shrink film derived from a polyester resin, characterized by comprising the following steps (1) to (2). Step (1): The step of preparing dicarboxylic acid compound and diol compound as reaction components and reacting them to produce polyester resin. Step (2): The step of stretching the polyester resin in a specified direction to produce a polyester heat-shrinkable film showing the following structures (a) to (c). (a) A crystallization peak containing the 2θ value obtained using an X-ray diffraction apparatus that shows the maximum value at a diffraction angle (between 42° and less than 44°) in the (-105) plane, and the half-width of the crystallization peak is less than 7°. (b) The crystal size of the (-105) plane obtained by X-ray diffraction is less than 2.5 nm. (c) When the heat shrinkage rate when shrinking in warm water at 80°C for 10 seconds is set as A1, A1 is a value in the range of 25% to 65%. By manufacturing in this way, even when applied to various PET bottles, it is possible to effectively produce polyester heat-shrinkable films that quantitatively suppress the generation of fine wrinkles.

[0015] In implementing the method for manufacturing the polyester heat shrinkable film of the present invention, it is preferable that, in step (2), at least the composition (a) and (b) are measured online. By measuring the composition (a) and (b) of at least the polyester heat shrink film online, the quality of the polyester heat shrink film can be easily and effectively determined during the manufacturing process. Simple Explanation of the Diagram

[0016] Figure 1 (a) to (c) are diagrams illustrating the morphology of polyester heat shrink film. [Figure 2] is a graph illustrating the relationship between the half-peak width (°) and crystal size (nm) obtained from XRD measurements of polyester heat-shrinkable films. [Figure 3] is a graph illustrating the relationship between the half-peak width (°) and refractive index (-) obtained from XRD measurements of polyester heat-shrinkable films. Figures (a) to (c) of [4] illustrate the relationship between the half-peak width (°) obtained from XRD measurements of polyester heat-shrinkable films and the heat shrinkage rates A1 (%) at 80°C, A2 (%) at 70°C, and A3 (%) at 100°C. [Figure 5] is a graph illustrating the relationship between half-peak width (°) and haze (relative value) obtained from XRD measurements of polyester heat-shrinkable films. [Figure 6] is a graph used to illustrate the relationship between crystal size (nm) and refractive index (-) obtained from XRD measurements of polyester heat-shrinkable films. Figures (a) to (c) of [7] illustrate the relationship between crystal size (nm) and heat shrinkage rates A1 (%) at 80°C, A2 (%) at 70°C, and A3 (%) at 100°C, obtained from XRD measurements of polyester heat shrink films. [Figure 8] is a diagram (photograph) showing the appearance of the cylindrical label without wrinkles, which is equivalent to Example 1. Figures (b) to (d) of Figure 8 are enlarged views of regions P, Q, and R of the appearance shown in Figure 8 (a). [Fig. 9] is a diagram (photograph) showing the appearance of the cylindrical label when wrinkles were formed, corresponding to Comparative Example 1. Fig. 9(b) to (d) are enlarged diagrams of regions S, T, and U of the appearance shown in Fig. 9(a), respectively. Implementation

[0017] [First Implementation Plan] The first embodiment is a polyester heat shrink film 10 as illustrated in Figure 1(a), which is a polyester heat shrink film 10 derived from a polyester resin. The feature is that when the main shrinkage direction is set as the TD direction and the direction orthogonal to the main shrinkage direction is set as the MD direction, the following configurations (a) to (c) are satisfied. (a) A crystallization peak containing the 2θ value obtained using an X-ray diffraction apparatus that shows the maximum value at a diffraction angle (between 42° and less than 44°) in the (-105) plane, and the half-width of the crystallization peak is less than 7°. (b) The crystal size of the (-105) plane obtained by X-ray diffraction is less than 2.5 nm. (c) When the heat shrinkage rate during heat shrinkage in warm water at 80°C for 10 seconds is set as A1, A1 is a value in the range of 25% to 65%. The polyester heat-shrinkable film of the first embodiment will be described in detail below with appropriate reference to the accompanying drawings.

[0018] 1. Polyester resin There is no particular limitation on the type of polyester resin constituting the polyester heat shrink film of the first embodiment. When the total amount of polyester resin is set to 100% by weight, it is generally preferred to be a polyester resin composition containing 30 to 100% by weight of non-crystalline polyester resin and 0 to 70% by weight of crystalline polyester resin.

[0019] (1) Non-crystalline polyester resin As a non-crystalline polyester resin, it can be used as long as it is a polymer derived primarily from polyols and dicarboxylic acids and is an amorphous polyester resin at room temperature. Therefore, a non-crystalline polyester resin formed from polyols and hydroxycarboxylic acids, a non-crystalline polyester resin formed from polyol dicarboxylic acids and hydroxycarboxylic acids, or a mixture of these polyester resins are preferred. In addition, whether it is a non-crystalline polyester resin can be determined by the fact that there is basically no melting peak of the crystalline part in the DSC curve obtained by using DSC (differential scanning calorimeter).

[0020] Here, the polyols used as raw material components of non-crystalline polyester resins can include at least one of aliphatic diols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol, and hexanediol, alicyclic diols such as 1,4-hexanediethanol, and aromatic diols. Therefore, among these polyols, ethylene glycol, diethylene glycol, and 1,4-hexanediethanol are particularly preferred. This is because, by using this polyol and reacting it appropriately with a polycarboxylic acid, it is easy to obtain a non-crystalline polyester resin whose non-crystalline properties are controlled to the desired state.

[0021] In addition, dicarboxylic acids that are raw material components of the same polyester resin can include at least one of 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 their ester-forming derivatives. Furthermore, terephthalic acid is particularly preferred. In addition, hydroxycarboxylic acids, which are also compounds of the same polyester resin, can include at least one of lactic acid, hydroxybutyric acid, polycaprolactone, etc.

[0022] (2) Crystalline polyester resin On the other hand, as a crystalline polyester resin, it can be used as long as it is a polyester resin that has a crystalline portion at room temperature. Therefore, polyester resins formed from polyols and dicarboxylic acids, polyester resins formed from polyols and hydroxycarboxylic acids, polyester resins formed from polyols, dicarboxylic acids and hydroxycarboxylic acids, or mixtures of these polyester resins are preferred. In addition, whether it is a crystalline polyester resin can be determined by the presence of a melting peak in the crystalline portion within a specified temperature range in the DSC curve obtained using a DSC (Differential Scanning Calorimeter).

[0023] Here, the polyols that are the compound components of polyester resins can be listed as at least one of the following: ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol, hexanediol and other aliphatic diols, alicyclic diols such as 1,4-hexanediethanol, aromatic diols and so on, which have the same reaction components as non-crystalline polyester resins. Therefore, ethylene glycol, diethylene glycol, and 1,4-hexanediethanol are particularly preferred. Furthermore, dicarboxylic acids that are the same reactive components of the same polyester resin can include 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 their ester-forming derivatives.

[0024] Therefore, as crystalline polyester resins, there are polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and polypropylene terephthalate, which can be used individually or as mixtures. In particular, as an example of a crystalline polyester resin, a crystalline polyester resin formed of 100 parts by weight of terephthalic acid and 100 parts by weight of ethylene glycol relative to the terephthalic acid can be appropriately used in the total amount of the reactants.

[0025] (3) Blending ratio The polyester resin composition constituting the polyester heat shrink film preferably comprises 20 to 100% by weight of amorphous polyester resin and 0 to 80% by weight of crystalline polyester resin relative to the total amount (100% by weight). The reason is that by limiting the amount of non-crystalline polyester resin and crystalline polyester resin blended in this way, although a portion undergoes phase separation, they can still be mixed uniformly, since it is sometimes difficult to adjust viscoelastic properties such as loss coefficient. Therefore, it is possible to easily adjust the thermal shrinkage rate or maximum shrinkage stress near the shrinkage temperature to the desired range, while also easily controlling the haze value quantitatively.

[0026] More specifically, this is because if the content of non-crystalline polyester resin is less than 20% by weight, it is sometimes difficult to adjust the viscoelastic properties such as the loss coefficient, and it is difficult to control the heat shrinkage rate, mechanical strength or maximum shrinkage stress of the polyester heat shrink film near the shrinkage temperature. Therefore, it is more preferable to include 50 to 90% by weight of non-crystalline polyester resin and 10 to 50% by weight of crystalline polyester resin relative to the total amount, and even more preferably to include 70 to 90% by weight of non-crystalline polyester resin and 10 to 30% by weight of crystalline polyester resin relative to the total amount.

[0027] 2. Composition (a) As a component (a) of a polyester heat-shrinkable film, (a) includes a crystalline peak whose 2θ value obtained by X-ray diffraction measurement device shows a maximum value at a diffraction angle (between 42° and less than 44°) in the (-105) plane, and the half-width of the crystalline peak is less than 7°. The reason is that, using an X-ray diffraction measuring device (transmitted light), which is a simple and precise measurement method, the full width at half maximum (FWHM) of the crystal peak corresponding to the (-105) plane can be limited to a narrow range of values ​​of 7° or less. Therefore, even when applied to various PET bottles, the generation of fine wrinkles can be quantitatively suppressed. Conversely, this is because, in the charts measured by X-ray diffraction (transmitted light) instruments, if the half-width of the crystallization peak exceeds 7°, it is difficult to control thermal shrinkage and quantitatively suppress the formation of fine wrinkles. However, if the half-peak width of the crystallization peak is made too narrow, the yield in manufacturing will be significantly reduced, or sometimes the types of polyester resins that can be used will be excessively restricted. Therefore, it is more preferable to limit the half-width at half-maximum (WHM) of the crystallization peak to a value in the range of 1 to 6.5°, and even more preferable to limit the WHM of the crystallization peak to a value in the range of 2 to 6°.

[0028] Here, Figure 2 is mentioned to illustrate the relationship between the half-peak width (°) of the crystallization peak and the crystal size (nm). That is, as can be understood from the characteristic curves in Figure 2, the following correlation exists: as the full width at half maximum (FWHM) increases, the crystal size decreases inversely. More specifically, it can be understood that there is a tendency for the crystal size to be in the range of 1.5 to 2.5 nm when the full width at half maximum (FWHM) is 3 to 5°, and below 1.5 nm when the FWHM exceeds 5°. Furthermore, when the FWHM exceeds 7°, the crystal size is below 1 nm. In fact, in the examples described later, a crystal size of 1.75 to 2.74 nm was obtained when the full width at half maximum (FWHM) was in the range of 3.25 to 5.07°. Therefore, although there are other influencing factors in the measurement charts obtained using X-ray diffraction equipment, the desired crystal size (below 2.5 nm) can be obtained by controlling the full width at half maximum (FWHM) of the crystallization peak within a specified range.

[0029] Next, Figure 3 is mentioned to illustrate the relationship between the half-peak width (°) of the crystallization peak and the refractive index (-) in the TD direction (hereinafter, sometimes simply referred to as the refractive index) in the measurement chart obtained using an X-ray diffraction apparatus. That is, as can be understood from the characteristic curves in Figure 3, the following correlation exists: as the full width at half maximum (FWHM) increases, the refractive index decreases exponentially. In fact, in the cases described later, when the half-width at half-maximum (WHM) is in the range of 3.25 to 5.07°, a refractive index of about 1.60 to 1.67 (-) is obtained, and when the WHM exceeds 7°, a refractive index of about 1.5 to 1.58 (-) is obtained. Therefore, although there are other influencing factors in the measurement chart obtained using X-ray diffraction equipment, the desired refractive index (the refractive index in the TD direction is 1.58~1.66) can be obtained by controlling the half-width of the crystallization peak within a specified range (e.g., 3~5°).

[0030] Next, referring to Figures 4(a) to (c), the relationship between the half-peak width (°) of the crystallization peak and the thermal shrinkage rates A1 (%) at 80℃, A2 (%) at 70℃, and A3 (%) at 100℃ will be explained respectively. That is, from the characteristic curves in Figure 4(a)~(c), it can be understood that there is the following tendency: as the half-peak width increases, the thermal shrinkage rate increases respectively, and then slowly decreases when the half-peak width exceeds 5~6°. In fact, in the examples described later, for the heat shrinkage rate A1 at 80°C, a value of about 30 to 60% can be obtained by making the half-peak width more than 4°. Similarly, for the thermal shrinkage rate A2 at 70°C, a value of about 15-35% can be obtained by making the half-peak width above 4°. Similarly, for the thermal shrinkage rate A3 at 100°C, a value of about 50-80% can be obtained by making the half-peak width above 4°. Therefore, it can be said that although there are still relationships with other influencing factors in the measurement charts obtained by using X-ray diffraction measurement devices, by controlling the half-peak width of the crystallization peak to a specified range (e.g., 3~5°), the thermal shrinkage rate of 70℃~100℃ can also be controlled to the desired range.

[0031] Next, Figure 5 is mentioned to illustrate the relationship between the half-peak width (°) of the crystallization peak and the haze (%) in the measurement chart obtained using the X-ray diffraction measuring device. That is, as can be understood from the characteristic curves in Figure 5, the following correlation exists: when the half-peak width is in the range of 3 to 5°, the haze value is in the range of about 1 to 5%, with a slight tendency to increase; when the half-peak width exceeds 5° and is in the range of 8°, the haze value decreases to below 3%. In fact, in the examples described later, when the half-peak width is in the range of 3.25 to 5.07°, a haze of about 1.60 to 5.2% is obtained, and when the half-peak width exceeds 7°, a haze of about 1.8% is obtained. Therefore, although there are other influencing factors in the measurement chart obtained using an X-ray diffraction measuring device, the desired haze can be obtained by controlling the half-peak width of the crystallization peak to a specified range (e.g., 3~5°).

[0032] 3. Composition (b) Furthermore, as a component (b) of a polyester heat-shrinkable film, it is characterized by a crystal size of 2.5 nm or less on the (-105) plane obtained by X-ray diffraction measurement. The reason is that, using an X-ray diffraction measuring device (transmitted light), which is a simple and precise measurement method, the crystal size of the (-105) plane can be limited to a relatively small value of less than 2.5 nm. Therefore, even when applied to various PET bottles, the generation of fine wrinkles can be quantitatively suppressed. Conversely, this is because if the crystal size exceeds 2.5 nm, it is difficult to control thermal shrinkage and quantitatively suppress the formation of fine wrinkles. However, if the crystal size is suppressed to an excessively small size, the manufacturing yield will be significantly reduced, or the types of polyester resins that can be used will be excessively restricted. Therefore, it is more preferable to limit the crystal size to a value in the range of 0.5 to 2.3, and even more preferable to limit the crystal size to a value in the range of 1.3 to 2.1.

[0033] Here, Figure 6 is mentioned to illustrate the relationship between crystal size (nm) and refractive index (-). That is, as can be understood from the characteristic curves in Figure 6, the following trend can be observed: when the crystal size is in the range of about 1.2~2.5nm, the refractive index increases proportionally; when the crystal size exceeds 2.5nm, the refractive index value is almost saturated. In fact, in the embodiments described later, when the crystal size is 1.2 to 2.45 nm, a refractive index of about 1.5 to 1.65 is obtained, and when the crystal size exceeds 2.5 nm and reaches 2.74 nm, the refractive index value increases to about 1.67. Therefore, by limiting the crystal size to a value within a specified range (e.g., below 2.5 nm), the desired refractive index value (e.g., 1.58 to 1.66) can be obtained.

[0034] Next, Figure 7 is mentioned, and the relationship between crystal size (nm) and thermal shrinkage rates A1 (%) at 80℃, A2 (%) at 70℃, and A3 (%) at 100℃ are explained respectively. That is, as can be understood from the characteristic curves in Figure 7, the following trend can be observed by judgment: when the crystal size is in the range of 1~2μm, the thermal shrinkage rate at 70℃~100℃ either increases slowly or remains at almost the same value; when the crystal size exceeds 2μm, the thermal shrinkage rate at 70℃~100℃ decreases rapidly. For example, in the case of the embodiments described later, for the heat shrinkage rate A1 at 80°C, a value in the range of about 30% to 60% can be obtained by making the crystal size about 1 to 2.5 nm. Similarly, for the thermal shrinkage rate A2 at 70°C, by making the crystal size about 1~2.5 nm, a value in the range of about 3~35% can be obtained. Furthermore, for a thermal shrinkage rate of 100°C A3, by making the crystal size approximately 1~2.5nm, a value in the range of approximately 40~80% can be obtained. Therefore, it can be said that by controlling the crystal size to a specified range (e.g., below 2.5 nm), the thermal shrinkage rate at 70°C to 100°C can also be limited to a desired range.

[0035] 4. Composition (c) As a component (c) of a polyester heat shrink film, it is characterized in that when the heat shrinkage rate is set as A1 when heat shrinking in warm water at 80°C for 10 seconds along the TD direction, the value of A1 is in the range of 25% to 65%. The reason is that, under the condition of heat shrinkage temperature, the desired heat shrinkage rate can be controlled at a common 80°C, thereby quantitatively suppressing the generation of fine wrinkles, etc. Conversely, this is because if the crystal size exceeds 2.5 nm, it is difficult to control thermal shrinkage and quantitatively suppress the formation of fine wrinkles. However, if the heat shrinkage rate A1 is less than 25%, or conversely, more than 65%, the manufacturing yield is significantly reduced, or sometimes the types of polyester resins that can be used are excessively restricted. Therefore, it is more preferable to limit the heat shrinkage rate A1 to a value in the range of 35% to 55%, and even more preferably to a value in the range of 38% to 50%.

[0036] 5. Composition (d) As a component (d) of a polyester-based heat-shrinkable film, it is characterized by having a refractive index in the TD direction within the range of 1.58 to 1.66. The reason is that by using a refractometer or similar device, which is a simple and precise measurement method, the refractive index in the TD direction can be limited to a relatively narrow range. Thus, even when applied to various PET bottles, the generation of fine wrinkles can be quantitatively suppressed. Conversely, this is because if the refractive index is less than 1.58 or greater than 1.66, it is difficult to control thermal shrinkage and quantitatively suppress the formation of fine wrinkles. Therefore, it is more preferable to limit the refractive index to a value in the range of 1.59 to 1.66, and even more preferable to limit the refractive index to a value in the range of 1.61 to 1.64.

[0037] 6. Composition (e) As a component (e) of a polyester heat-shrinkable film, it is preferable that the heat shrinkage rate when heat-shrinking in warm water at 70°C for 10 seconds along the TD direction is set as A2, and A2 is a value in the range of 3 to 40%. The reason is that by limiting the heat shrinkage rate at 70°C, the polyester heat shrink film can obtain a good heat shrinkage rate during heat shrinkage, and thus it is also easy to obtain the maximum shrinkage stress. Therefore, the heat shrinkage rate at 70°C in the TD direction is more preferably a value in the range of 5 to 30%, and even more preferably a value in the range of 10 to 20%.

[0038] 7. Composition (f) As a component (f) of a polyester heat-shrinkable film, it is preferable to set the heat shrinkage rate when heat-shrinking in boiling water at 100°C for 10 seconds along the TD direction as A3, where A3 is a value in the range of 30% to 80%. The reason is that by limiting the heat shrinkage rate at 100°C, the polyester heat shrink film can obtain a good heat shrinkage rate during heat shrinkage, and thus it is also easy to obtain the maximum shrinkage stress. Therefore, the heat shrinkage rate at 100°C in the TD direction is more preferably in the range of 40% to 75%, and even more preferably in the range of 45% to 73%.

[0039] 8. Composition (g) As a component (g), the haze value measured according to JIS K 7136:2000 is preferably 10% or less. By controlling the haze value within the specified range in this way, not only is the transparency excellent, but the printability or uniform heat shrinkage can also be achieved. However, if the haze value is too low, the types or amounts of polymerizable components that can be used will be limited, making manufacturing difficult to control and resulting in excessively low production efficiency. Therefore, the haze value is more preferably in the range of 1 to 8%, and even more preferably in the range of 2 to 5%.

[0040] 9. Thickness The thickness of polyester heat shrink film is usually preferably in the range of 10 to 100 μm. The reason is that by specifically limiting the film thickness before heat shrinkage to a value within a specified range, it is easy to manufacture a uniform thickness, while it is easy to control the heat shrinkage rate or maximum shrinkage stress, and it is easy to prevent uneven shrinkage. Therefore, the film thickness before heat shrinkage is more preferably in the range of 20 to 60 μm, and even more preferably in the range of 30 to 50 μm.

[0041] 10. Other thermal properties, etc. (1) Thermal shrinkage rate in the MD direction 1 In polyester heat shrink film, the constituent element is that the direction orthogonal to the main shrinkage direction is set as the MD direction, and the heat shrinkage rate (B1) of the MD direction when shrinking at a temperature of 80°C for 10 seconds is less than 5%. The reason is that by limiting the 80°C heat shrinkage rate in the MD direction to less than 5%, a good heat shrinkage rate in the main shrinkage direction can be obtained in the polyester heat shrink film during heat shrinkage, and thus it is also easy to obtain the maximum shrinkage stress. Therefore, the thermal shrinkage rate at 80°C in the MD direction is more preferably a value of 3% or less, and even more preferably a value of 1% or less.

[0042] (2) Thermal shrinkage rate in the MD direction 2 In polyester heat shrink film, the constituent element is that the direction orthogonal to the main shrinkage direction is set as the MD direction, and the heat shrinkage rate (B2) of the MD direction when shrinking under the condition of 90°C and 10 seconds is less than 10%. The reason is that by limiting the 90°C heat shrinkage rate in the MD direction to less than 10%, a good heat shrinkage rate can be obtained in the polyester heat shrink film during heat shrinkage, and it is also easy to obtain the maximum shrinkage stress. Therefore, the thermal shrinkage rate at 90°C in the MD direction is more preferably 8% or less, and even more preferably 5% or less.

[0043] (3) Composition of polyester heat shrink film It is preferred that various additives be incorporated into or attached to a polyester heat shrink film, either on one or both sides. More specifically, relative to the total amount of polyester heat shrink film, it is generally preferred to blend at least one of the following in the range of 0.01 to 10% by weight: anti-hydrolysis agent, antistatic agent, ultraviolet absorber, infrared absorber, colorant, organic filler, inorganic filler, organic fiber, inorganic fiber, etc., and more preferably in the range of 0.1 to 1% by weight.

[0044] Furthermore, as shown in FIG1(b), it is also preferable to laminate other resin layers 10a, 10b containing at least one of the above-mentioned additives on one or both sides of the polyester heat shrink film 10. In this case, when the thickness of the polyester heat shrink film is set to 100%, it is generally preferable to set the single-layer thickness or total thickness of the additional resin layers to a value in the range of 0.1% to 10%.

[0045] 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 acrylic resin, olefin resin, urethane resin, rubber resin, etc., which are different from the polyester shrink film.

[0046] Furthermore, it is also preferable to make the polyester heat shrink film into a multi-layer structure to further achieve hydrolysis resistance and mechanical protection; or as shown in Figure 1(c), a shrinkage adjustment layer 10c is provided on the surface of the polyester heat shrink film 10 in such a way that the shrinkage rate of the polyester heat shrink film becomes uniform in the plane. The shrinkage adjustment layer can be laminated according to the shrinkage characteristics of the polyester heat shrink film by means of adhesives, coating methods or heat treatment.

[0047] More specifically, the thickness of the shrinkage adjustment layer is in the range of 0.1~3μm. When the shrinkage of the polyester heat shrinkage film at a specified temperature is too large, it is preferable to laminate a shrinkage adjustment layer of the type that suppresses it. 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 expands it. Therefore, polyester heat shrink film aims to achieve the desired shrinkage rate through a shrinkage rate adjustment layer, rather than by producing various heat shrink films with different shrinkage rates.

[0048] [Second Implementation Plan] The second embodiment is a method for manufacturing a polyester heat shrink film 10, which is the method for manufacturing a polyester heat shrink film 10 illustrated in FIG1(a), etc., characterized by having at least the following steps (1) to (2). Step (1): The step of preparing dicarboxylic acid compound and diol compound as reaction components and reacting them to produce polyester resin. Step (2): The polyester resin is stretched in a specified direction to produce a polyester heat shrink film 10 showing the following configurations (a) to (c). (a) A crystallization peak containing the 2θ value obtained using an X-ray diffraction apparatus that shows the maximum value at a diffraction angle (between 42° and less than 44°) in the (-105) plane, and the half-width of the crystallization peak is less than 7°. (b) The crystal size of the (-105) plane obtained by X-ray diffraction is less than 2.5 nm. (c) When the heat shrinkage rate when shrinking in warm water at 80°C for 10 seconds is set as A1, A1 is a value in the range of 25% to 65%. The manufacturing method of the polyester heat shrink film of the second embodiment will be described in detail below with appropriate reference to the accompanying drawings.

[0049] 1. Raw material preparation and mixing steps First, select crystalline polyester resin, non-crystalline polyester resin, rubber-based resin, antistatic agent, anti-hydrolysis agent and other main agents or additives as raw materials. Next, preferably, the prepared crystalline polyester resin or non-crystalline polyester resin is weighed and added into the mixing container, and then mixed and stirred until uniform using a stirring device.

[0050] 2. Raw material sheet manufacturing steps Next, it is preferable to dry the uniformly mixed raw materials to an absolutely dry state. Next, typically, extrusion molding is preferred to produce raw material sheets of a specified thickness. More specifically, for example, extrusion molding can be performed using an extruder (manufactured by TANABE PLASTICS MACHINERY CO., LTD.) with an L / D of 24 and an extrusion screw diameter of 50 mm at an extrusion temperature of 230~270°C, thereby obtaining raw material sheets of a specified thickness (typically 30~1000μm).

[0051] 3. Fabrication of Polyester-Based Heat Shrink Film Next, the obtained raw material sheet is moved on or between rollers using a heat shrink film manufacturing device, and heated and extruded at the same time to produce 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 extrusion are performed and stretched in a specified direction, thereby enabling the polyester molecules constituting the polyester heat shrink film to crystallize into a specified shape. Then, it is solidified in this state, thereby enabling the production of heat-shrinkable polyester heat-shrinkable films for use as decorations or labels, etc.

[0052] 4. Next, it is preferable to set an inspection step to show and confirm whether the polyester heat shrink film constituting (a) to (c) is shown. That is, a specified polyester heat-shrinkable film is prepared as the test object, and an X-ray diffraction measuring device is used to check and confirm the half-peak width or crystal size of the crystallization peak, as well as the heat shrinkage rate under specified heat shrinkage conditions within a specified range. Thus, even when applied to various PET bottles, the generation of fine wrinkles can be suppressed. Furthermore, since components (a) to (b) can be inspected using an X-ray diffraction measuring device, the manufacturing process of polyester heat-shrinkable film can be measured and managed online. At this point, it is preferable to confirm beforehand whether the thickness of the polyester heat shrink film is within the specified range.

[0053] 5. Other The obtained polyester heat shrink film is subjected to heat treatment using a specified heating device, or by immersion in hot water at a specified temperature and time (or immersion in hot water at a specified temperature and time), or by heat treatment, to cause the polyester heat shrink film to shrink, and the heat shrinkage rate is measured. In addition, it is preferable to pre-measure the haze, glass transition temperature or various thermal properties of the polyester heat shrink film and check whether they are within the specified range. Then, preferably, the obtained polyester heat shrink film is installed on a substrate such as a PET bottle, and in this state, it is heat-treated under specified conditions, and the uniform shrinkage of the polyester heat shrink film is evaluated.

[0054] In addition, for the polyester heat shrink film produced, the following characteristics should be measured continuously or intermittently to confirm whether they are within the specified range. It is preferable to set up inspection steps. That is, by following the prescribed inspection steps, the following characteristics are measured and it is confirmed whether they fall within the prescribed range, thereby achieving more uniform heat shrinkage characteristics, and enabling quantitative quality management even when heat shrinkage conditions change. 1) Visual inspection of the appearance of polyester heat shrink film 2) Measurement of thickness variation 3) Haze Measurement 4) Determination of glass transition temperature 5) Determination of melting point and heat of fusion 6) Determination of tensile modulus of elasticity 7) Tear strength test 8) SS curve determination

[0055] [Third Implementation Plan] The third implementation scheme is an implementation scheme related to the method of using the polyester heat shrink film in the first implementation scheme. That is, it is possible to appropriately apply any known method of using heat shrink film. For example, when implementing the method of using polyester heat shrink film, the polyester heat shrink film is first cut into appropriate lengths or widths to form long cylindrical objects. Next, the long cylindrical object is fed to an automatic labeling device (shrink labeler) to be further cut to the required length, and then inserted into PET bottles or similar containers filled with contents.

[0056] Next, as a heat treatment for the polyester heat shrink film embedded in PET bottles, etc., it is passed through the interior of a hot air channel or steam channel at a specified temperature. Then, the polyester heat-shrinkable film is uniformly heated and heat-shrinkable by the infrared radiation and other heat radiant heat provided by the aforementioned channel or by the heating steam blown from the surroundings at around 80°C. Therefore, when the half-peak width of the crystallization peak is less than 7°, as shown in Figures 8(a) to (d), it can be tightly adhered to the outer surface of PET bottles, etc., to quickly obtain a labeled container. On the other hand, when the half-peak width of the crystallization peak exceeds 7°, as shown in Figures 9(a) to (d), an area where the label cannot follow the shape around the bottle is generated from the upper to the lower part of the bottle body, and wrinkles are also significantly observed.

[0057] Example The present invention will now be described in detail based on embodiments. However, unless otherwise specified, the scope of the present invention is not limited by the description of the embodiments. In addition, the polyester resin used in Example 1, etc., is described below.

[0058] (PETG1) A non-crystalline polyester formed from 100 mol% dicarboxylic acid: terephthalic acid, 69 mol% glycol: ethylene glycol, 20 mol% 1,4-cyclohexanediethanol, and 11 mol% diethylene glycol. (PETG2) An amorphous polyester (glass transition temperature: 69°C) formed from 100 mol% dicarboxylic acid: terephthalic acid, 63 mol% glycol: ethylene glycol, 24 mol% 1,4-cyclohexanediethanol, and 13 mol% diethylene glycol. (APET) A crystalline polyester (glass transition temperature: none, intrinsic viscosity: 0.65 dL / g) formed from 100 moles of dicarboxylic acid: terephthalic acid and 100 moles of glycol: ethylene glycol. (additive) The silica masterbatch (manufactured by Sumika Color Co., Ltd., trade name "EPM-7E325") was used, which is composed of a matrix resin of PET, a silica content of 5% by mass, and an average silica particle size of 2.7 μm.

[0059] [Example 1] 1. Fabrication of polyester heat shrink film In a mixing vessel, non-crystalline polyester resin (PETG1) is contained in a ratio of 70 parts by weight (equivalent to 70 parts by weight when the total amount of the mixture is set to 100% by weight), and crystalline polyester resin (APET1) is contained in a ratio of 30 parts by weight (equivalent to 30 parts by weight when the total amount of the mixture is set to 100% by weight). The mixture is then stirred and used as raw material. Next, the raw material is dried to a completely dry state, and then extruded at an extruder (manufactured by TANABE PLASTICS MACHINERY CO., LTD.) with an L / D ratio of 24 and an extrusion screw diameter of 50 mm at an extrusion temperature of 260°C to obtain a raw material sheet.

[0060] Next, using a heat shrink film manufacturing apparatus, a polyester heat shrink film with a thickness of 40μm is produced from the raw material sheet under the conditions of a preheating temperature of 75°C, a stretching temperature of 75°C, a stretching ratio (MD direction: 100%, TD direction: 500%), and a heat setting temperature of 60°C.

[0061] 2. Evaluation of Polyester-Based Heat Shrink Film (1) Evaluation 1: Half-peak width On graphs obtained using an X-ray diffraction apparatus (Rigaku Corporation., RINT-RAPID, transmission method), the full width at half maximum (FWHM) of the crystallization peak showing the maximum 2θ value at diffraction angles (above 42° to below 44°) in the (-105) plane was determined. The results are shown in Table 2.

[0062] (2) Evaluation 2: Crystal size The crystal size of the (-105) plane was determined based on the graphs obtained using the X-ray diffraction apparatus described above. The results are shown in Table 2.

[0063] (3) Evaluation 3: Thermal shrinkage rate (A1) The heat shrinkage rate A1 was measured when the water was heated in warm water at 80°C for 10 seconds along the TD direction, and the heat 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

[0064] (4) Evaluation 4: Refractive Index The refractive index of the film in the TD direction was determined using a refractometer according to JIS K7142:2014. The results are shown in Table 2.

[0065] (5) Evaluation 5: Thermal shrinkage rate (A2) In Evaluation 5, except that the heat shrinkage conditions of Evaluation 3 (80°C, 10 seconds) were changed to 70°C, 10 seconds, the heat shrinkage rate (A2) in the TD direction of the polyester heat shrink film was also measured. The results are shown in Table 2.

[0066] (6) Evaluation 6: Thermal shrinkage rate (A3) In Evaluation 6, except that the heat shrinkage conditions of Evaluation 3 (80°C, 10 seconds) were changed to 100°C, 10 seconds, the heat shrinkage rate (A3) in the TD direction of the polyester heat shrink film was also measured. The results are shown in Table 2.

[0067] (7) Evaluation 7: Haze value The haze value of the obtained polyester heat shrink film was determined according to JIS K 7136:2000. The results are shown in Table 2.

[0068] (8) Evaluation 8: Anti-wrinkle properties In Evaluation 8, the wrinkle resistance (sometimes called the adhesion evaluation) of the polyester heat-shrinkable film after heat shrinkage was determined and evaluated according to the following criteria. That is, a cylindrical PET bottle (capacity: 500ml) filled with commercially available beverage water is prepared. Next, perforations with a width of 1 mm are made along the long side of the heat shrink film obtained by cutting the polyester heat shrink film into strips with a width of 26 cm, and 1,3-dioxolane is coated at 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. Then, the cylindrical label is cut every 16 cm along the long side to obtain multiple cylindrical labels. Next, the cylindrical label is placed on the body of the prepared cylindrical PET bottle and moved in a steam channel maintained at 85°C at a throughput speed of 6 m / min on a conveyor belt. The cylindrical label is heat-shrinked in a way that it fits tightly against the upper and lower parts of the cylindrical PET bottle body. Next, the heat-shrinked cylindrical labels were visually observed, and their 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. The results are shown in Table 2. ◎: No prescribed wrinkles were observed in any of the five cylindrical labels. ○: Of the 5 tubular labels, no prescribed wrinkles were observed in 3 or more. △: In 5 tubular labels, no prescribed wrinkles were observed in more than 1 of them. ×: In all 5 tubular labels, the production of the specified wrinkles was observed.

[0069] [Examples 2-5] In Examples 2-5, as shown in Table 1, the type of polyester resin and manufacturing conditions were changed, and various polyester-based heat-shrinkable films were prepared in the same manner as in Example 1. The half-peak width, crystal size, and heat shrinkage rate (A1-A3) of the crystallization peak were measured in the same manner as in Example 1. The results are shown in Tables 1-2.

[0070] [Comparative Examples 1-2] In Comparative Examples 1 and 2, as shown in Table 1, the type of polyester resin and manufacturing conditions were changed, and various polyester-based heat-shrinkable films were prepared in the same manner as in Example 1. The half-peak width of the crystallization peak, crystal size, heat shrinkage rate (A1~A3) and other parameters were measured.

[0071]

[0072] Evaluation 1: Half-peak width Evaluation 2: Crystal size Evaluation 3: Thermal shrinkage rate (A1) Evaluation 4: Refractive Index Evaluation 5: Thermal shrinkage rate (A2) Evaluation 6: Heat shrinkage rate (A3) Rating 7: Haze Value Rating 8: Anti-wrinkle properties

[0073] Industrial applicability According to the present invention, in a polyester heat-shrinkable film derived from a specified polyester resin composition, by measuring the half-width at a specified diffraction angle, crystal size, and heat shrinkage rate of the crystal peak at which the 2θ value shows its maximum value on a graph obtained using an X-ray diffraction measuring device (transmission method), and controlling them respectively within a specified range, heat shrinkage properties or wrinkle-resistant properties can be effectively and accurately managed. Therefore, the polyester heat shrink film according to the present invention can be applied to various PET bottles, etc., which can significantly broaden its versatility and has extremely high industrial applicability.

[0074] 10: Polyester heat shrink film 10a: Other resin layers 1 10b: Other resin layers 2 10c: Shrinkage adjustment layer

Claims

1. A polyester-based heat-shrinkable film, which is a polyester-based heat-shrinkable film derived from a polyester resin formed by the reaction of a dicarboxylic acid compound and a diol compound, wherein when the main shrinkage direction is set as the TD direction and the direction orthogonal to the main shrinkage direction is set as the MD direction, the polyester-based heat-shrinkable film satisfies the following configurations (a) to (c): (a) a crystallization peak that shows the maximum value at a diffraction angle (between 42° and less than 44°) in the (-105) plane obtained by X-ray diffraction measurement device, and the half-width of the crystallization peak is less than 7°; (b) the crystal size in the (-105) plane obtained by X-ray diffraction measurement device is less than 2.5 nm; (c) when the heat shrinkage rate when heat-shrinking in warm water at 80°C for 10 seconds along the TD direction is set as A1, the A1 is a value in the range of 25% to 65%.

2. The polyester heat shrinkable film as claimed in claim 1, which satisfies the following configuration (d), (d) the refractive index in the TD direction is in the range of 1.58 to 1.66 as determined according to JIS K7142:2014.

3. The polyester heat shrink film as described in claim 1, which satisfies the following configuration (e), where (e) is a value in the range of 3 to 40% when the heat shrinkage rate when heat-shrinking in warm water at 70°C for 10 seconds along the TD direction is set as A2.

4. The polyester heat shrink film as described in claim 1, which satisfies the following configuration (f), wherein when the heat shrinkage rate of (f) when heat shrinking in warm water at 100°C for 10 seconds along the TD direction is set to A3, the value of A3 is in the range of 30% to 80%.

5. The polyester heat shrinkable film as described in claim 1, which satisfies the following composition (g): (g) has a haze value of 10% or less as determined according to JIS K 7136:2000.

6. The polyester heat-shrinkable film as described in claim 1, having a thickness in the range of 10 to 100 μm.

7. A method for manufacturing a polyester heat shrink film, which is a method for manufacturing a polyester heat shrink film derived from a polyester resin, comprising the following steps (1) to (2): Step (1): preparing a dicarboxylic acid compound and a diol compound as reaction components and reacting them to manufacture the polyester resin; Step (2): stretching the polyester resin in a predetermined direction to produce a polyester heat shrink film exhibiting the following components (a) to (c): (a) a crystallization peak exhibiting the maximum value at a diffraction angle (between 42° and less than 44°) on the (-105) plane obtained by an X-ray diffraction measuring device, wherein the half-width of the crystallization peak is less than 7°; (b) a crystal size on the (-105) plane obtained by the X-ray diffraction measuring device is less than 2.5 nm; (c) when the heat shrinkage rate when shrinking in warm water at 80°C for 10 seconds is set as A1, A1 is a value in the range of 25% to 65%.

8. A method for manufacturing a polyester heat-shrinkable film as claimed in claim 7, wherein in step (2), the composition (a) and (b) are measured online.

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