Packaging and packaging containers

Abstract

To provide a package using a heat-shrinkable polyester film that is substantially free of amorphous components, or a packaging container having the same on at least a part of the outer periphery of the container. [Solution] A packaging body in which a ring-shaped body cut according to the object to be packaged and with both ends of the film adhered thereto is heat-shrunk to cover at least a portion of the outer periphery of the object to be packaged, and the heat-shrinkable polyester film that serves as the base material (1) contains 90 mol % or more of ethylene terephthalate units in 100 mol % of all ester units, (2) has a melting peak during the temperature rise process in a differential scanning calorimeter (DSC), with the peak temperature, or melting point (Tm), being 200°C or more and 280°C or less, and the heat of fusion (ΔHm), which is the peak area, being 40 J / g or more and 60 J / g or less, and (3) a peak of heat shrinkage appears in the circumferential direction of the object to be packaged, with the heat shrinkage at the peak being 1% or more and 40% or less.

Description

[Technical Field]

[0001] The present invention relates to a package after heat shrinkage of a heat shrinkable polyester film and a packaging container covered with this package. [Background technology]

[0002] In recent years, stretched films (so-called heat-shrinkable films) made of polyvinyl chloride resins, polystyrene resins, and polyester resins have been used for applications such as label packaging, cap seals, and stacked packaging that combine the protection and product labeling of glass or plastic bottles, as well as banding for containers such as lunch boxes. Among these heat-shrinkable films, polyvinyl chloride films have problems such as low heat resistance, the generation of hydrogen chloride gas when incinerated, and the production of dioxins. Polystyrene films, on the other hand, have poor solvent resistance, require the use of inks with special compositions for printing, and require incineration at high temperatures, resulting in the generation of large amounts of black smoke accompanied by an unpleasant odor upon incineration. On the other hand, polyester heat-shrinkable films are widely used as heat-shrinkable labels due to their high heat resistance, ease of incineration, and excellent solvent resistance. Their use is on the rise as the distribution of PET (polyethylene terephthalate) bottles and other products increases. In recent years, there has been a growing trend to reuse used PET bottles in light of environmental issues and the effective use of resources. For example, Patent Document 1 discloses an example of a polyester film made from 80% by weight of PET resin recycled from PET bottles (recycled PET).

[0003] However, the labels using the film disclosed in Patent Document 1 (recycled PET labels) do not have heat shrinkability and cannot be attached to bottles, so they have been used only for certain cylindrical bottles, etc. In other words, recycled PET labels have had problems with poor design and range of application compared to heat-shrinkable polyester films.

[0004] On the other hand, conventional heat-shrinkable polyester films generally use amorphous polyester raw materials (amorphous raw materials), as described in Patent Document 2, for example. This is because it is believed that amorphous molecules are involved in the expression of shrinkage. For example, the examples in Patent Document 2 show a tendency for shrinkage to increase as the content of the monomer that constitutes the amorphous component increases. However, heat-shrinkable polyester films made from amorphous raw materials cannot be recycled together with PET bottles because their resin composition differs from that of PET bottles. This is because recycling films made from amorphous raw materials together with PET bottles not only changes the composition of the recycled PET, but also causes extrusion defects when crushed bottles are melted and solidified during the recycling process due to the different thermal properties of the PET bottles and labels. Current recycling methods require crushing used PET bottles together with their labels, followed by alkaline washing and a separation process (e.g., a float-sink method using water) that utilizes the difference in specific gravity between the bottles and labels. Furthermore, when a heat-shrinkable polyester film made from an amorphous material is used as a label, there is a problem that labels block together when the contents to be packaged are hot (e.g., hot beverages). Regarding this problem, for example, Patent Document 3 discloses a technology that can prevent blocking by providing an anti-blocking layer on at least one side of a polyester base film. However, even when an anti-blocking layer is provided on the surface of the film, there is still a problem with recyclability. That is, because the anti-blocking layer has a different composition from the container, the label still needs to be removed. Therefore, a label that combines anti-blocking and recyclability is desired.

[0005] When using a heat-shrinkable film as a bottle label, a typical method involves fixing the ends of the film together with a solvent, adhesive, or the like to form a ring-shaped (tube-shaped) label, which is then placed over the bottle and shrunk. Shrinking the film across the width is efficient because it allows shrink labels to be produced continuously. Therefore, Patent Document 4 discloses a heat-shrinkable film that undergoes heat shrinkage in the transverse (width) direction but hardly any heat shrinkage in the longitudinal (lengthwise) direction, and a method for producing the same. In the examples of Patent Document 4, a film that exhibits the desired heat shrinkage properties is produced by using polyethylene terephthalate as the raw material and uniaxially stretching the film that has been wrinkled in the longitudinal direction.

[0006] Furthermore, the applicant of the present application has disclosed in Patent Document 5 a heat-shrinkable polyester film that has sufficient heat shrinkage properties in the main shrinkage direction, which is the longitudinal direction (machine direction), even if it does not contain a large amount of monomer components that can become amorphous components, and that has a low heat shrinkage rate in the width direction (vertical direction) perpendicular to the main shrinkage direction, and has small thickness unevenness in the longitudinal direction. Patent Document 5 describes a method for producing a polyester-based unstretched film, the main constituent of which is ethylene terephthalate, with a content of 0 to 5 mol % of a monomer component that can become an amorphous component in the total polyester resin components, by a biaxial stretching method in which the film is stretched laterally and then longitudinally. For example, as stretching method A, a simultaneous biaxial stretching machine as shown in FIG. 1 is used to stretch the film in the width direction (transverse stretching) at a ratio of 3.5 to 6 times at a temperature of the film's Tg or higher (Tg + 40°C) or lower, and then, by widening the clip spacing at a temperature of the film's Tg or higher (Tg + 40°C) or lower, the film is stretched in the longitudinal direction (longitudinal stretching) at a ratio of 1.5 to 2.5 times, while narrowing the tenter width by 5 to 30% after the transverse stretching to relax the film in the width direction. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6150125 [Patent Document 2] Japanese Patent Application Publication No. 8-27260 [Patent Document 3] Patent No. 5564753 [Patent Document 4] Japanese Patent Application Publication No. 5-169535 [Patent Document 5] International Publication No. 2015 / 118968 [Non-patent literature]

[0008] [Non-Patent Document 1] Yuji Mariya, "Mechanism of Fiber Structure Formation and Development of High-Performance Fibers," Journal of the Society of Fiber Science and Technology (Fiber and Industry), Vol. 63, No. 12 (2007) [Non-patent document 2] A. Mahendrasingam et al “Effect of draw ratio and temperature on the strain induced crystallization of poly (ethylene terephthalate) at fast draw rates” Polym. 40 5556 (1999) Summary of the Invention [Problem to be solved by the invention]

[0009] As mentioned above, Patent Document 4 discloses a heat-shrinkable film that shrinks significantly in the width direction. However, in the examples of Patent Document 4, the heat shrinkage rate in the width direction at 95°C is at most 12.5%, which is difficult to say meets the level of shrinkage rate required for current heat-shrinkable films.

[0010] On the other hand, the heat-shrinkable polyester film described in Patent Document 5 has a longitudinal direction as its main shrinkage direction. Therefore, a film having a high heat shrinkage rate in the width direction and small thickness unevenness has not yet been disclosed, among films having a width direction as its main shrinkage direction. Even if the transverse-to-longitudinal stretching method described in Patent Document 5 is simply changed to longitudinal-to-transverse stretching, relaxation in the non-shrinkage direction (longitudinal direction) cannot be achieved, resulting in a high shrinkage rate in the longitudinal direction, and the desired film cannot be obtained. Furthermore, even if the stretching method is changed from longitudinal to transverse, there is a risk that the heat shrinkage stress in the width direction will also increase.

[0011] The present invention has been made in view of the above circumstances, and its object is to provide a packaging body in which an annular body is covered with a heat-shrinkable polyester film that is substantially free of amorphous components, or a packaging container having the same on at least a part of the outer periphery of the container, and to provide a packaging body in which an annular body is covered with a heat-shrinkable polyester film that has a high circumferential heat shrinkage rate for the annular body, an excellent appearance after shrinkage, and excellent heat blocking resistance, and that can be recycled together with containers such as PET bottles, or a packaging container having the same on at least a part of the outer periphery of the container. [Means for solving the problem]

[0012] The present invention has the following features that solve the above problems. 1. A packaging body in which a ring-shaped body made of a heat-shrinkable polyester film as a base material, with both ends of the film adhered, covers at least a portion of the outer periphery of an object to be packaged in a heat-shrunk state, and the covered ring-shaped body satisfies the following requirements (1) to (3). (1) The heat-shrinkable polyester film used as the base material contains 90 mol % or more of ethylene terephthalate units in 100 mol % of all ester units. (2) The heat-shrinkable polyester film used as the base material has a melting peak during the temperature rise process in a differential scanning calorimeter (DSC), and the peak temperature, i.e., the melting point (Tm), is 200°C or higher and 280°C or lower, and the heat of fusion (ΔHm), i.e., the peak area, is 40J / g or higher and 60J / g or lower. (3) In the circumferential direction of the packaged object, the peak of the heat shrinkage rate of the heat-shrinkable polyester film used as the base material, as determined by thermomechanical analysis (TMA), appears between 60°C and 120°C, and the heat shrinkage rate at that peak is between 1% and 40%. 2. The package according to 1, characterized in that the peel strength of the adhesive portion of the coated annular body is 2N / 15mm or more and 15N / 15mm or less. 3. The package according to 1 or 2, wherein the intrinsic viscosity (IV) of the heat-shrinkable polyester film serving as the base material is 0.5 dL / g or more and 0.8 dL / g or less. 4. The package according to any one of 1 to 3, wherein the adhesion is achieved by an organic solvent composition. 5. The package according to 4, wherein the organic solvent composition contains a polymer component. 6. A packaging container characterized by having the packaging body according to any one of 1 to 5 on at least a part of the outer periphery of the container. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a package that is substantially free of amorphous components, has a high heat shrinkage rate in the width direction (i.e., the circumferential direction of the annular body), which is the main shrinkage direction of the heat-shrinkable polyester film, has excellent appearance after shrinkage, and is covered with an annular body that has excellent heat-blocking properties. Therefore, it becomes possible to recycle the package together with the container, which not only increases recycling productivity but also contributes to improving the quality of recycled PET. [Brief explanation of the drawings]

[0014] [Figure 1] 1 shows the thermal shrinkage rates obtained by TMA for the packages of Example 1 and Comparative Example 1. [Figure 2] 1 shows DSC curves of the heat-shrinkable polyester film used as the base material for the packaging bodies of Example 1 and Comparative Example 3, and of the PET bottle. DETAILED DESCRIPTION OF THE INVENTION

[0015] 1.Packaging The packaging of the present invention is formed by covering at least a portion of the outer periphery of an object to be packaged with a ring-shaped body made of a heat-shrinkable polyester film as a base material and then heat-shrinking the body. Examples of the object to be packaged include PET beverage bottles, various bottles, cans, plastic containers for confectionery and lunch boxes, and paper boxes (hereinafter collectively referred to as the object to be packaged). The packaging body that covers the object to be packaged may or may not be printed, and may have perforations or notches in a direction perpendicular to the circumferential direction, which is the main shrinkage direction of the ring-shaped body (hereinafter sometimes referred to as the label). Furthermore, the label of the present invention may be printed or unprinted. However, as an evaluation method, in order to eliminate measurement disturbances of the label's printed layer, only the film base without the label's printed layer may be measured. In other words, an unprinted label is itself a film base, while a printed label may be evaluated as only the transparent film base by wiping the printed layer with an organic solvent, for example. This is sometimes referred to hereinafter as the "film base excluding the printed layer." Considering that the annular body of the present invention (including the printed layer) is used for applications such as bottle labels and as a banding film for bundling lunch boxes, the thickness of the annular body is preferably 5 μm to 200 μm, more preferably 20 μm to 150 μm. A thickness of more than 200 μm is uneconomical because it simply increases the weight per area of ​​the film. On the other hand, a thickness of less than 5 μm makes the film extremely thin, making it difficult to handle (poor handling) during processes such as forming the annular body.

[0016] 1.1. Heat shrinkage rate of packaging The annular body (film substrate excluding the printing layer) coated onto the container of the present invention preferably exhibits a peak heat shrinkage temperature of 60°C or higher and 120°C or lower, as determined by thermomechanical analysis (TMA), with the heat shrinkage at the peak being 1% or higher and 40% or lower. The heat shrinkage of the coated annular body refers to the heat shrinkage remaining after heat shrinking the heat-shrinkable polyester film. This can be rephrased as the heat shrinkage consumed when the heat-shrinkable polyester film is heat-shrunk to coat the container using the method described below. A peak heat shrinkage temperature of the coated annular body higher than 120°C indicates that the temperature used to shrink the film onto the container was higher than the appropriate temperature, which tends to deteriorate the shrinkage finish. If the peak heat shrinkage temperature of the coated annular body is lower than 60°C, the film is likely to shrink (change in dimensions) after being used as a package (even at room temperature), which not only tends to reduce the design of the package but also tends to cause deformation of the container due to tight wrapping, which is undesirable. The peak temperature of the heat shrinkage of the coated annular body is more preferably 65°C or higher and 115°C or lower, and even more preferably 70°C or higher and 120°C or lower.

[0017] Furthermore, if the heat shrinkage rate of the coated annular body at the peak temperature is higher than 40%, the shrinkage consumption rate will be small when heat-shrunk onto a container, making it difficult for the coated annular body to adhere to the container. Poor adhesion to the container is undesirable because it is prone to causing poor appearance, such as wrinkles and pockmarks, on the coated annular body. On the other hand, if the heat shrinkage rate of the coated annular body is less than 1%, this means that the film heat-shrinks excessively onto the container, making the container more likely to deform and also prone to vertical sink marks and wrinkles on the coated annular body (label). This is also undesirable because it is prone to causing poor appearance. It is even more preferable for the heat shrinkage rate of the coated annular body to be between 2% and 35%.

[0018] 1.2. Melting point (Tm) and heat of fusion (ΔHm) of coated annular bodies The annular body (film substrate excluding the printed layer) coated on the container of the present invention has an endothermic peak (melting peak) appearing in a temperature range of 140°C or higher in a thermogram obtained by heating from 40°C to 300°C at a heating rate of 10°C / min using a differential scanning calorimeter (DSC), and the peak temperature, i.e., melting point (Tm), is preferably 200°C to 280°C, and the peak area, i.e., heat of fusion (ΔHm), is preferably 40 J / g to 60 J / g. When heated from room temperature to 300°C at a heating rate of 10°C / min using a DSC, the Tm of a PET bottle is approximately 255°C, and the ΔHm is approximately 50 J / g. Large deviations from these thermal properties are undesirable because they can easily cause problems when the PET bottle is crushed, melted, and solidified for recycling. Specifically, if the Tm of the coated cyclic body is less than 200°C or the ΔHm is less than 40 J / g, problems such as the resin sticking to the screw (so-called winding) are likely to occur when melted together with the PET bottle in the extrusion process. Furthermore, the above problems are also likely to occur when the coated cyclic body does not exhibit a melting peak. On the other hand, if the Tm of the packaging body is higher than 280°C or the ΔHm is higher than 60 J / g, the heat required to melt the coated cyclic body when melted together with the PET bottle in the extrusion process is insufficient, increasing the possibility of extrusion stopping due to a sudden increase in extrusion pressure. The Tm of the coated cyclic body is more preferably 205°C to 275°C, and even more preferably 210°C to 270°C. The ΔHm of the coated cyclic body is more preferably 42 J / g to 58 J / g, and even more preferably 44 J / g to 56 J / g.

[0019] 1.3.Method of coating a container with an annular body 1.3.1. Method for forming the ring body In order to cover an object to be packaged with a heat-shrinkable polyester film, it is preferable to adopt a method in which a ring-shaped body is formed in advance so that the main shrinkage direction is the circumferential direction, and then the ring-shaped body is placed over the object to be packaged and heat-shrunk. When forming the ring-shaped body, in addition to a method in which the heat-shrinkable polyester film is bonded using various adhesives, it is also possible to use a method in which the heat-shrinkable polyester film is fused and bonded using a high-temperature heating element (for example, a heat sealing method, an impulse sealing method, or a fusion sealing method). When forming a ring-shaped body using an adhesive, it is preferable to overlap and bond both ends of the heat-shrinkable polyester film. Here, "end" refers to the end in the width direction (longitudinal direction), including the position within 20 mm from the end. Conventionally, when forming a ring-shaped body from a heat-shrinkable film made from an amorphous raw material, solvents such as 1,3-dioxolane and tetrahydrofuran have been used as adhesive solvents. However, heat-shrinkable polyester films containing more than 90 mol% ethylene terephthalate units among all ester units, as in the present invention, are difficult to dissolve with solvents alone, making it difficult to achieve high adhesive strength. While bonding is possible using a hot melt adhesive made by melting a polyester resin, the heat of the hot melt causes the film to shrink and wrinkle, leading to poor appearance. Furthermore, due to the high viscosity of hot melt, it is difficult to consistently apply a constant amount of adhesive to the film during the adhesive application process, and stability decreases as the production speed increases. Therefore, in the present invention, it is preferable to use an adhesive solvent composition, in which a polymer composition is contained in a solvent (medium), as the adhesive for forming the annular body, since this can overcome the above drawbacks.

[0020] The solvent used in the adhesive solvent composition may be a good solvent that has high solubility in the polymer composition. Specific examples include 1,3-dioxolane, tetrahydrofuran, toluene, 1,4-dioxane, 1,2,2,2-tetrachloroethane, benzene, and xylene. Among these, 1,3-dioxolane and tetrahydrofuran are preferred due to their high solubility in the polymer composition, and 1,3-dioxolane is particularly preferred due to its highest solubility. Furthermore, for purposes such as adjusting the adhesive strength of the cyclic bodies, a poor solvent that has low solubility in the polymer composition may be mixed with the good solvent. Specific examples of poor solvents include acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, and propyl acetate. These good solvents and poor solvents may be used alone or in a mixed state as long as they are capable of dissolving the polymer composition. The polymer composition used in the adhesive-solvent composition is preferably a polyester whose main constituent is ethylene terephthalate units. Here, "mainly composed of ethylene terephthalate units" refers to a polyester containing 50 mol% or more of ethylene terephthalate units relative to the total amount of polyester constituents. However, because this increases chemical resistance and reduces solubility in organic solvents such as 1,3-dioxolane, the ethylene terephthalate units are preferably 70 mol% or less, and more preferably 60 mol% or less, of the 100 mol% of the polyester constituent units. Furthermore, the ethylene terephthalate units are preferably 5 mol% or more, and more preferably 10 mol% or more, of the 100 mol% of the polyester constituent units.

[0021] Examples of dicarboxylic acid components other than terephthalic acid that constitute the polyester used in the adhesive solvent composition include aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, and orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid, and alicyclic dicarboxylic acids. Examples of diol components other than ethylene glycol that constitute the polyester used in the adhesive solvent composition include aliphatic diols such as 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol; and aromatic diols such as bisphenol A. The polyester used in the adhesive solvent composition is preferably a polyester containing one or more of aromatic dicarboxylic acids such as isophthalic acid, aliphatic dicarboxylic acids such as adipic acid, cyclic diols such as 1,4-cyclohexanedimethanol, and diols having 3 or more carbon atoms (for example, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, hexanediol, etc.), and having a glass transition point (Tg) of 70°C or less. Furthermore, the polyester used in the adhesive-solvent composition has one or more monomer components that can be amorphous components in 100 mol % of the polycarboxylic acid components or 100 mol % of the polyhydric alcohol components in the entire polyester resin, in total, of 30 mol % or more, preferably 40 mol % or more, and more preferably 50 mol % or more. If the total amount of monomer components that can be amorphous components is less than 30 mol %, the solubility in organic solvents such as 1,3-dioxolane is low, and the composition cannot be used as an adhesive solvent.

[0022] Examples of monomers that can become amorphous components include isophthalic acid, orthophthalic acid, adipic acid, sebacic acid, 1,4-cyclohexanedimethanol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, and hexanediol. The upper limit of the polyester content in the adhesive / solvent composition is 25% by mass or less, preferably 20% by mass or less, and more preferably 15% by mass or less. This is because the higher the polyester content in the adhesive / solvent composition, the higher the viscosity of the adhesive / solvent composition, making it difficult to stably apply a constant amount of the adhesive / solvent composition to the film during the process of adhering the film edges. The lower limit of the polyester content in the adhesive / solvent composition is 1% by mass or more, preferably 2% by mass or more. If the polyester content in the adhesive / solvent composition is less than 1% by mass, sufficient peel strength cannot be obtained when adhering a polyester film containing more than 25% by mass of polyethylene terephthalate. If necessary, various additives, such as viscosity reducers, heat stabilizers, coloring pigments, coloring inhibitors, and ultraviolet absorbers, may be added to the adhesive-solvent composition. There is no particular lower limit to the viscosity of the adhesive solvent composition, but if the viscosity is too low, it becomes difficult to stably apply a constant amount in the bonding step, so it is preferably 100 mPa·s or less.

[0023] In the bonding step, it is preferable to apply the adhesive solvent composition to the film in an amount of about 50 to 550 mg / m2 using a known center seal machine, etc. The width of the adhesive solvent composition to be applied in the bonding step is preferably 1 mm or more to prevent peeling of the adhesive portion, and although there is no particular upper limit, it is preferably 10 mm or less because the smaller the label area used, the lower the cost. The speed of the bonding step is not particularly limited, but 300 to 500 m / min is preferable in terms of high speed. After the bonding step, the annular body is usually folded flat and wound into a roll, and then the annular body is unwound and cut to a predetermined length to become a final product. However, when making the final product, a cutting step may be performed after the bonding step without winding onto a roll.

[0024] The coated annular body of the present invention preferably has a peel strength of 2 N / 15 mm or more at the solvent-bonded portion, more preferably 3 N / 15 mm or more, and particularly preferably 4 N / 15 mm or more. A peel strength of 2 N / 15 mm or more can prevent problems such as the coated annular body peeling off from the container. Furthermore, in the coated annular body of the present invention, the upper limit of the peel strength of the solvent-bonded portion is less than 15 N / 15 mm. The higher the peel strength, the more preferable, but in the present invention, 15 N / 15 mm was the technical limit. The adhesive strength was measured according to the method described in the Examples.

[0025] When heat-shrinkable polyester film is fusion-sealed, a method can be used in which a predetermined automatic bag-making machine (e.g., RP500 manufactured by Kyoei Printing Machinery Materials Co., Ltd.) is used to adjust the temperature and angle of the fusion blade to predetermined conditions (e.g., fusion blade temperature = 240°C, blade angle = 70°) and form ring-shaped or bag-shaped bodies at a predetermined speed (e.g., 100 pieces / min). Note that, in the present invention, bag-shaped bodies are also considered to be ring-shaped bodies. Additionally, when labeling an object to be packaged, a method can be used in which the film constituting the ring-shaped body is wrapped around the object to be packaged, the overlapping portion is fusion-sealed, and the ring-shaped body is then wrapped around the object to be packaged, followed by heat shrinkage.

[0026] 1.3.2.Heat shrinking onto containers Known methods can be used to cover a container with the ring-shaped body prepared as described above. That is, the container covered with the ring-shaped body before heat shrinking is placed on a belt conveyor or the like and transported into a tunnel through which a heat medium is blown out, thereby heat-shrinking the ring-shaped body and covering the package. The method of covering the container with the ring-shaped body before heat shrinking can be manual or mechanical, and is not limited thereto. Steam or hot air is used as the heat medium; the former is called a steam tunnel, and the latter is called a hot air tunnel. As the heat medium, either steam or hot air can be used alone, or two types can be used by connecting these tunnels. Furthermore, it is preferable for the tunnel to have two or more connected zones with different temperature ranges, as this tends to improve the finish quality after the package is shrunk onto the container. When multiple zones with different temperature ranges are provided, setting the first zone at a low temperature and gradually increasing the temperature in subsequent zones is a particularly preferred method, as this improves the finish quality. The label heat-shrinks as it passes through these tunnels, thereby covering the container with the heat-shrunk ring-shaped body. The package of the present invention refers to the package after heat shrinking.

[0027] The temperature inside the tunnel when thermally shrinking the annular body is preferably 50°C or higher and 120°C or lower in the case of a steam tunnel, and 60°C or higher and 230°C or lower in the case of a hot air tunnel. Temperatures lower than the respective lower limit temperatures are undesirable because the maximum thermal shrinkage stress in the width direction of the package is likely to exceed 10 MPa, making the appearance more likely to be poor. Temperatures higher than the respective upper limit temperatures are undesirable because the maximum thermal shrinkage stress in the width direction of the package is likely to fall below 1 MPa, making the appearance more likely to be poor. A more preferable temperature is 55°C or higher and 115°C or lower in the case of a steam tunnel, and 65°C or higher and 225°C or lower in the case of a hot air tunnel. The residence time when passing through the tunnel is preferably 5 to 60 seconds. A residence time of 5 seconds or less is undesirable because the heat shrinkage rate of the package tends to exceed 40%, making it more likely to cause poor appearance. On the other hand, a residence time of 60 seconds or less is undesirable because the heat shrinkage rate of the package tends to fall below 1%, making it more likely to cause poor appearance. The residence time in the tunnel is more preferably 10 to 55 seconds, and even more preferably 15 to 50 seconds. Usually, when a container is covered with an annular body, the packaging body is heat-shrunk by about 2 to 30% to be tightly attached to the object to be packaged. Note that the present invention also includes a packaging container having the label of the present invention on at least a part of the outer periphery of the container.

[0028] 1.4. Intrinsic viscosity (IV) of the package The intrinsic viscosity (IV) of the annular body (film substrate excluding the printed layer) coated on the container of the present invention is preferably in the range of 0.5 to 0.8. If the annular body has an IV of less than 0.5, the effect of improving tear resistance will be reduced and cracks will be more likely to occur during transportation, which is undesirable. On the other hand, if the IV is greater than 0.8, the filter pressure will increase significantly during melt extrusion in the film-forming process of the substrate film, making high-precision filtration difficult. The intrinsic viscosity is more preferably 0.52 or more and 0.78 or less.

[0029] 2. Polyester raw materials used in heat-shrinkable polyester films The polyester raw material used in the heat-shrinkable polyester film of the present invention contains ethylene terephthalate units in an amount of 90 mol % or more out of 100 mol % of all ester units, preferably 95 mol % or more, and most preferably 100 mol %. The ethylene terephthalate units contain ethylene glycol and terephthalic acid as main components. By using ethylene terephthalate, the heat-shrinkable polyester film can achieve excellent heat resistance and transparency, and the melting point Tm and heat of fusion ΔHm can be made closer to those of PET bottles. The polyester raw material used in the present invention may contain amorphous components (amorphous alcohol components and amorphous acid components), but the sum of the proportion of amorphous alcohol components in 100 mol% of all alcohol components and the proportion of amorphous acid components in 100 mol% of all acid components is controlled to be 0 mol% or more and 5 mol% or less. Containing more than 5 mol% of amorphous components can cause problems such as the melting peak becoming less apparent, the melting point Tm being more likely to be less than 200°C, and the heat of fusion ΔHm being more likely to be less than 40 J / g. These problems can be solved by limiting the amorphous component content to 5 mol% or less. As described above, in the present invention, a polyester consisting solely of ethylene terephthalate units is preferred, but they are not actively copolymerized, and constituent units of terephthalic acid and diethylene glycol may be present as by-products in the ethylene terephthalate units. The lower the content of amorphous components, the better, with 0 mol% being the most preferred.

[0030] Examples of the amorphous acid component (carboxylic acid component) monomer include isophthalic acid, 1,4-cyclohexanedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid. Furthermore, examples of monomers for the amorphous alcohol component (diol component) include neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, and hexanediol. The polyester raw material used in the present invention may contain 1,4-butanediol, a diol component other than ethylene glycol, as a component other than the above-mentioned ethylene terephthalate and amorphous component. 1,4-butanediol lowers the melting point of the polyester film and is useful as a low-Tg component, but within the scope of the present invention, it is preferable to avoid its inclusion as much as possible. By limiting the 1,4-butanediol content to 10 mol% or less, the melting point Tm and heat of fusion ΔHm can be made closer to those of PET bottles. The content of 1,4-butanediol relative to the total alcohol components and total acid components is preferably 10 mol% or less, more preferably 5 mol% or less, and most preferably 0 mol%.

[0031] Various additives may be added to the polyester raw material used in the present invention as needed. The additives are not particularly limited, and examples thereof include known additives such as waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducers, heat stabilizers, coloring pigments, color inhibitors, and ultraviolet absorbers. Furthermore, it is preferable to add fine particles that act as a lubricant to the polyester raw material in order to improve the workability (slipperiness) of the film. The fine particles can be selected from any type, regardless of whether they are inorganic or organic. Examples of inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate. Examples of organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, and cross-linked polystyrene particles. The average particle size of the fine particles, as measured with a Coulter counter, is preferably within the range of approximately 0.05 to 3.0 μm. The method of blending the above-mentioned fine particles into the above-mentioned polyester raw material is not particularly limited, and for example, it can be added at any stage of producing a polyester resin, but it is preferable to add the fine particles as a slurry dispersed in ethylene glycol or the like at the stage of esterification, or after the completion of transesterification reaction and before the start of polycondensation reaction, and then proceed with the polycondensation reaction.Also, it may be performed by a method of blending a slurry of the fine particles dispersed in ethylene glycol or water or the like with the polyester resin raw material using a vented kneading extruder; or a method of blending dried fine particles with the polyester resin raw material using a kneading extruder.

[0032] The intrinsic viscosity (IV) of the polyester raw material is preferably in the range of 0.5 to 0.8. If the IV is lower than 0.5, the effect of improving tear resistance decreases and cracks tend to occur during transport as a package, which is undesirable. On the other hand, if the IV is higher than 0.8, the increase in filtration pressure becomes large, making high-precision filtration difficult. The intrinsic viscosity is more preferably 0.52 or more and 0.78 or less. The heat-shrinkable polyester film of the present invention may be subjected to corona treatment, coating treatment, flame treatment, or the like in order to improve the printability and adhesiveness of the film surface.

[0033] 3. Characteristics of heat-shrinkable polyester film When the heat-shrinkable polyester film used in the annular body of the present invention is used for bottle labels, the temperatures that contribute most to the shrink finish of the label are 90°C in the width direction and 70°C and 90°C in the length direction, and controlling the shrinkage rate in these temperature ranges is technically more difficult than in other temperature ranges. The present invention is extremely useful in that it is possible to use a heat-shrinkable polyester film that has a very high heat shrinkage rate in the width direction, which is the main shrinkage direction, and a low heat shrinkage rate in the length direction, and that has little thickness unevenness, as an annular body. 3.1 Thermal shrinkage rate in the width direction The heat-shrinkable polyester film used in the annular body of the present invention preferably has a shrinkage rate in the width direction (main shrinkage direction) of 50% to 75% when immersed in hot water at 90°C for 10 seconds. Here, the "width direction" refers to the direction perpendicular to the longitudinal direction (machine direction; MD) and is also called the transverse direction (TD). A heat shrinkage rate in the width direction at 90°C of less than 50% is not preferred because, when the film is shrunk to cover a container or the like, the film does not shrink sufficiently, resulting in poor adhesion to the container and poor appearance. On the other hand, a heat shrinkage rate in the width direction at 90°C of more than 75% is not preferred because, when the film is shrunk to cover a container or the like, the shrinkage rate becomes extremely fast, resulting in distortion of the film. The heat shrinkage rate in the width direction at 90°C is more preferably 55% to 70%, and even more preferably 60% to 65%.

[0034] 3.2.Heat shrinkage rate in the longitudinal direction The heat-shrinkable polyester film used in the annular body of the present invention preferably has a heat shrinkage rate in the longitudinal direction (machine direction, MD) when immersed in 90°C hot water for 10 seconds of -6% or more and 14% or less. If the heat shrinkage rate in the longitudinal direction at 90°C is less than -6%, excessive elongation occurs when the film is shrunk to cover a container or the like, which makes it prone to wrinkling and makes it difficult to obtain a good shrink appearance, which is undesirable. On the other hand, if the heat shrinkage rate in the longitudinal direction at 90°C exceeds 14%, distortion and sink marks are likely to occur after shrinkage, which is undesirable. The heat shrinkage rate in the longitudinal direction at 90°C is more preferably -4% or more and 12% or less, and even more preferably -2% or more and 10% or less. Furthermore, the heat-shrinkable polyester film used in the annular body of the present invention preferably has a heat shrinkage rate in the longitudinal direction (machine direction, MD) of -6% or more and 6% or less when immersed in hot water at 70°C for 10 seconds. If the heat shrinkage rate in the longitudinal direction at 70°C is less than -6%, excessive elongation occurs when the film is shrunk to cover a container or the like, which makes it prone to wrinkling and makes it difficult to obtain a good shrink appearance, which is undesirable. On the other hand, if the heat shrinkage rate in the longitudinal direction at 70°C exceeds 6%, distortion and sink marks are likely to occur after shrinkage, which is undesirable. The heat shrinkage rate in the longitudinal direction at 70°C is more preferably -4% or more and 4% or less, and even more preferably -2% or more and 2% or less.

[0035] 3.3. Uneven thickness in the width direction The heat-shrinkable polyester film used in the annular body of the present invention preferably has a thickness variation of 1% to 20% across the width when measured over a length of 1 m. A thickness variation of more than 20% across the width is undesirable because it not only causes poor appearance such as edge misalignment and wrinkles when the film is wound into a roll, but also makes printing defects more likely to occur when the film is printed. The thickness variation across the length is more preferably 19% or less, and even more preferably 18% or less. The smaller the thickness variation across the width, the better, but considering the performance of the film-forming equipment, it is considered that the limit is about 1%.

[0036] 3.4. Maximum heat shrinkage stress in the width direction The heat-shrinkable polyester film used in the annular body of the present invention preferably has a maximum heat shrinkage stress in the shrinking direction obtained by TMA (transverse mechanical analysis) of 4 MPa or more and 13 MPa or less before heat shrinkage. During heat shrinkage, if the maximum heat shrinkage stress in the width direction exceeds 13 MPa, the packaged object, such as a container, will be prone to deformation, which is undesirable. On the other hand, if the maximum heat shrinkage stress in the width direction is below 4 MPa, the degree of adhesion to the container will decrease during heat shrinkage, which will deteriorate the finish after shrinkage, which is undesirable. The maximum heat shrinkage stress in the width direction before heat shrinkage is more preferably 5 MPa to 12 MPa, and even more preferably 6 MPa to 11 MPa.

[0037] 3.5. Crystallinity calculated from density The heat-shrinkable polyester film used in the annular body of the present invention preferably has a crystallinity calculated from density of 1% to 15%. If the crystallinity exceeds 15%, the heat shrinkage rate in the width direction increases. The relationship between the heat shrinkage rate in the width direction and the crystallinity will be described later. The lower the crystallinity, the better, since the heat shrinkage rate in the width direction increases; 13% or less is more preferable, and 11% or less is even more preferable. Note that the lower limit of the crystallinity at the current technical level is about 1%. The method for measuring the crystallinity is described in the Examples section.

[0038] 3.6. Other Characteristics The thickness of the heat-shrinkable polyester film (film substrate excluding the printed layer) used in the present invention for the ring-shaped body is preferably 5 μm to 200 μm, more preferably 20 μm to 150 μm, considering that it will be used for bottle labels or as a banding film for bundling lunch boxes, etc. A thickness of more than 200 μm simply increases the weight per area of ​​the film, which is uneconomical. On the other hand, a thickness of less than 5 μm makes the film extremely thin, making it difficult to handle (poor handling) during processes such as forming the ring-shaped body. The haze value is preferably 2% or more and 13% or less. A haze value exceeding 13% is undesirable because it results in poor transparency and may result in poor appearance when producing labels. The haze value is more preferably 11% or less, and even more preferably 9% or less. Although a smaller haze value is preferable, taking into consideration the necessity of adding a certain amount of lubricant to the film in order to impart the necessary slipperiness for practical use, the lower limit is about 2%.

[0039] 4. Manufacturing method of heat-shrinkable polyester film for use in annular body The heat-shrinkable polyester film used in the annular body of the present invention can be produced by transversely stretching an unstretched film obtained by melt-extruding the raw materials described in 2. Heat-shrinkable polyester film using an extruder under the following conditions. Specifically, the film is preheated at a temperature (T1) of (Tg + 40°C) or more but not exceeding (Tg + 70°C), the preheated film is transversely stretched at a temperature (T2) of (Tg + 5°C) or more but not exceeding (Tg + 40°C), and the transversely stretched film is further stretched at a temperature (T3) of (Tg - 10°C) or more but not exceeding (Tg + 15°C). The T1, T2, and T3 satisfy the relationship T1 > T2 > T3. If necessary, after the second transverse stretching at T3, heat treatment may be performed at a temperature of (Tg - 30°C) or more but not exceeding Tg. The polyester can be obtained by polycondensing the aforementioned suitable dicarboxylic acid component and diol component using a known method. Generally, two or more types of polyester chips are mixed together and used as a raw material for film. Each step will be described in detail below.

[0040] 4.1.Melt extrusion When melt-extruding the raw resin, it is preferable to dry the polyester raw material using a dryer such as a hopper dryer or paddle dryer, or a vacuum dryer. After drying the polyester raw material in this way, it is melted at a temperature of 200 to 300°C using an extruder and extruded into a film. For extrusion, any existing method such as a T-die method or a tubular method can be used. The extruded sheet-like molten resin can then be rapidly cooled to obtain an unstretched film. A preferred method for rapidly cooling the molten resin is to cast the molten resin from a die onto a rotating drum and rapidly cool and solidify it to obtain a substantially unoriented resin sheet. The resulting unstretched film is stretched in the width (transverse) direction by the method described in detail below, thereby obtaining a heat-shrinkable polyester film to be used for the annular body of the present invention.

[0041] 4.2. Lateral stretching Hereinafter, the stretching method for obtaining the heat-shrinkable polyester film to be used in the annular body of the present invention will be described in detail, taking into consideration the differences in molecular structure from conventional methods for producing heat-shrinkable polyester films and from Non-Patent Documents 1 and 2. Although many details about the molecular structure that governs the shrinkage behavior of films remain unclear, it is generally believed that oriented amorphous molecules are responsible for the shrinkage characteristics. Therefore, heat-shrinkable polyester films are typically produced by stretching amorphous raw materials in the desired shrinkage direction (the main shrinkage direction, usually the width direction). Conventional heat-shrinkable polyester films made from amorphous raw materials are typically produced by stretching at temperatures between the glass transition temperature (Tg) and Tg + 30°C at a stretch ratio (final stretch ratio) of approximately 3.5 to 5.5 times. These stretching conditions are thought to orient the amorphous molecules and impart shrinkage to the film; the lower the stretching temperature or the higher the stretch ratio, the higher the shrinkage (i.e., the easier it is for the amorphous molecules to become oriented). On the other hand, when the heat-shrinkable polyester film used in the annular body of the present invention contains substantially no amorphous raw material, i.e., 0 mol% to 5 mol% of a monomer component that can become an amorphous component, and is stretched at the same temperature as above, i.e., at a temperature of Tg to Tg + 30°C, the film shrinks when stretched at a magnification of 2 to 2.5 times, but the shrinkage rate of the film decreases when stretched at the same magnification as above, i.e., about 3.5 to 5.5 times. For example, Comparative Examples 1 and 3 in Table 1 below are examples of films produced using a polyester raw material with a Tg of 75°C, stretched transversely at 3.6 times (Comparative Example 1) or 2.4 times (Comparative Example 3) at a temperature of 85 to 90°C (Comparative Example 1) or 80°C (Comparative Example 3). In Comparative Example 3, where the stretching ratio was as low as 2.4 times, the shrinkage rate in the width direction was as high as 55.3%, but in Comparative Example 1, where the stretching ratio was as high as 3.6 times, the shrinkage rate in the width direction was significantly reduced to 26.8%.

[0042] This is thought to be because the oriented molecules crystallize (oriented crystallization) upon stretching, inhibiting film shrinkage (i.e., shrinkage of amorphous molecules). For example, Figure 4 in Non-Patent Document 1 shows the relationship between stress (horizontal axis) and birefringence (vertical axis) during uniaxial stretching of polyethylene terephthalate fibers, and the changes in molecular orientation can be seen from this figure. Specifically, in the range of stretching ratios DR up to approximately 2x, stress and birefringence are linearly related, and when stretching is stopped, stress is relieved and birefringence decreases. The decrease in birefringence indicates relaxation of molecular chains, and in the case of a film, this is thought to indicate film shrinkage (the occurrence of shrinkage). On the other hand, when the stretching ratio DR exceeds 2x, the linear relationship between stress and birefringence becomes difficult to establish, and no decrease in birefringence is observed even when stretching is stopped. This phenomenon is thought to indicate a decrease in shrinkage due to oriented crystallization. Therefore, even if the film does not substantially contain amorphous raw materials, as in the present invention, it is thought that a shrinkage rate can be exhibited in the film under conditions where oriented crystallization due to stretching does not occur.

[0043] Here, the stretching conditions under which stretching does not result in orientation crystallization are shown, for example, in the photograph in Figure 2 of Non-Patent Document 2. This shows that a crystalline peak was observed when stretching at a low temperature of 85°C (= Tg + 10°C), whereas no crystalline peak was observed when stretching at a high temperature of approximately 130°C (= Tg + 55°C), indicating that the molecules were not oriented or crystallized at all. This is thought to be because the rate of molecular relaxation during high-temperature stretching is faster than the rate of orientation. In fact, when the inventors performed high-temperature stretching at a constant temperature of 130°C on a film production line, no shrinkage was observed because the molecules were not oriented, as explained by the above mechanism. Furthermore, not only was no shrinkage observed, but it was also found that thickness unevenness was poor (increased) due to the lack of increase in stress during stretching. Therefore, the inventors discovered that by dividing the stretching process into a step in which the molecules are hardly oriented by high-temperature stretching and a step in which the molecules are actively oriented by low-temperature stretching, rather than performing the entire stretching process at a constant high temperature as described above, it is possible to suppress the decrease in shrinkage due to oriented crystallization, while orienting only amorphous molecules to achieve the desired shrinkage and to reduce thickness unevenness, leading to the completion of the present invention. Specifically, as described in detail below, by preheating at temperature T1, stretching transversely at temperature T2, and then stretching transversely at temperature T3 (T1>T2>T3), it was found that only amorphous molecules are present in the film, allowing the thermal shrinkage in the longitudinal and width directions to be controlled and thickness unevenness in the width direction to be reduced.

[0044] Each step will be explained below in order. First, the preheating zone is preheated at a temperature T1 between (Tg + 40°C) and (Tg + 70°C). If the preheating temperature T1 is less than (Tg + 40°C), the molecules are likely to be oriented and crystallized during the transverse stretching in the subsequent step T2, resulting in a thermal shrinkage percentage in the width direction of the film that is likely to fall below the lower limit of 50% (see Comparative Example 1 in Table 1 below). Furthermore, if the preheating temperature T1 is less than (Tg + 40°C), the neck-in caused by transverse stretching increases the stress applied in the machine direction, making the thermal shrinkage percentage in the machine direction likely to exceed the upper limit of 6%, which is undesirable. On the other hand, if the preheating temperature T1 exceeds (Tg + 70°C), thickness unevenness in the width direction worsens, making it likely to exceed the upper limit of 20%, which is undesirable. The preheating temperature T1 is more preferably between (Tg + 45°C) and (Tg + 65°C), and even more preferably between (Tg + 50°C) and (Tg + 60°C). Specifically, it is preferable to control the passage time through the preheating zone to between 2 and 10 seconds so that the preheating temperature T1 is reached. If the passage time through the preheating zone is less than 2 seconds, transverse stretching in the next step T2 will begin before the film reaches the preheating temperature T1. This will result in the same problems as when the preheating temperature T1 is less than (Tg + 40°C). A longer passage time through the preheating zone is preferable because it makes it easier for the film temperature to reach the preheating temperature T1. However, if the passage time is too long, the preheating zone temperature will be set above the cold crystallization temperature, which will excessively promote crystallization of the unstretched film, which is undesirable. Furthermore, a longer passage time through the preheating zone is undesirable because it requires more production equipment. A passage time through the preheating zone of 10 seconds is sufficient.

[0045] Next, the film preheated at the temperature T1 is transversely stretched at a temperature T2 between (Tg + 5°C) and (Tg + 40°C) (sometimes referred to as the first transverse stretching). As mentioned above, the first transverse stretching requires suppressing molecular orientation due to stretching, so the temperature T2 during the first transverse stretching is controlled to be lower than the preheating temperature T1 and between (Tg + 5°C) and (Tg + 40°C). If the temperature T2 during the first transverse stretching is less than (Tg + 5°C), the same problems as those during preheating occur, and the thermal shrinkage in the film width direction is likely to fall below the lower limit of 50% and the thermal shrinkage in the longitudinal direction is likely to exceed the upper limit of 6%, which is undesirable. On the other hand, if the temperature T2 during the first transverse stretching exceeds (Tg + 40°C), the thickness unevenness in the width direction is likely to exceed the upper limit of 20%, which is undesirable. The temperature T2 in the first transverse stretching is more preferably (Tg+10°C) or more and (Tg+35°C) or less, and even more preferably (Tg+15°C) or more and (Tg+30°C) or less. Furthermore, the stretching ratio in the first transverse stretching is preferably 1.5 times or more and 2.5 times or less. If the stretching ratio in the first transverse stretching is less than 1.5 times, the effect of suppressing oriented crystallization will be reduced, and the shrinkage ratio in the film width direction will likely fall below 50% and the shrinkage ratio in the longitudinal direction will likely exceed 6%, which is undesirable. On the other hand, if the stretching ratio in the first transverse stretching is more than 5 times, thickness unevenness in the width direction will likely exceed 20%, which is undesirable. The stretching ratio in the first transverse stretching is more preferably 1.6 times or more and 2.4 times or less, and even more preferably 1.7 times or more and 2.3 times or less.

[0046] The transversely stretched film is further stretched at a temperature T3 of (Tg - 10°C) or more (Tg + 15°C) or less (sometimes referred to as second transverse stretching). As mentioned above, in the first transverse stretching, stretching is performed at a high temperature to suppress molecular orientation, but in the subsequent second transverse stretching, on the other hand, it is necessary to actively induce molecular orientation by stretching. Therefore, in the present invention, stretching is performed at a low temperature so that T2 > T3, and specifically, the temperature T3 in the second transverse stretching is (Tg - 10°C) or more (Tg + 15°C or less). If the temperature T3 in the second transverse stretching is lower than (Tg - 10°C), the stress applied in the machine direction due to neck-in caused by transverse stretching increases, and the thermal shrinkage in the machine direction is likely to exceed the upper limit of 6%, which is undesirable. On the other hand, if the temperature T3 in the second transverse stretching exceeds (Tg + 15°C), the molecular orientation will be reduced, and the thermal shrinkage in the width direction will likely fall below the lower limit of 50% (see Comparative Example 5 in Table 1 below). The temperature T3 in the second transverse stretching is more preferably (Tg - 7°C) or higher (Tg + 12°C) or lower, and even more preferably (Tg - 4°C) or higher (Tg + 9°C) or lower.

[0047] The stretching ratio in the second transverse stretching is preferably 1.5 to 2.5 times. If the stretching ratio in the second transverse stretching is less than 1.5 times, thickness unevenness in the width direction will worsen. On the other hand, if the stretching ratio in the second transverse stretching is more than 2.5 times, not only will the shrinkage rate in the width direction be easily reduced, but the shrinkage stress in the width direction will also increase. The stretching ratio in the second transverse stretching is more preferably 1.6 to 2.4 times, and even more preferably 1.7 to 2.3 times. The final stretching ratio (the product of the stretching ratio in the first transverse stretching and the stretching ratio in the second transverse stretching) is preferably 3 to 5.5 times. If the final stretching ratio is less than 3 times, not only is the shrinkage rate in the width direction likely to decrease, but thickness unevenness in the width direction also worsens. On the other hand, if the final stretching ratio exceeds 5.5 times, breakage is likely to occur during stretching in the width direction. The final stretching ratio is more preferably 3.1 to 5.4 times, and even more preferably 3.2 to 5.3 times. In the heat-shrinkable polyester film used in the annular body of the present invention, the preheating temperature T1, the temperature T2 in the first stretching, and the temperature T3 in the second stretching satisfy the relationship T1>T2>T3. If transverse stretching is performed so that each of T1, T2, and T3 satisfies the above-mentioned range while satisfying this relationship, a desired film can be obtained.

[0048] 4.3.Heat Treatment The film stretched transversely as described above may be heat-treated in a tenter while both edges in the width direction are held with clips, if necessary. Here, heat treatment means heat treatment at a temperature of (Tg-20°C) or higher and Tg or lower for 1 to 9 seconds. This heat treatment is preferably used because it can suppress a decrease in the heat shrinkage rate and improves dimensional stability after storage over time. If the heat treatment temperature is lower than (Tg-20°C), the above-mentioned effects of the heat treatment are not effectively exhibited. On the other hand, if the heat treatment temperature is higher than Tg, the heat shrinkage rate in the width direction is likely to fall below the lower limit of 50%. The temperature during the heat treatment is preferably equal to or lower than the temperature T3 during the second stretching. Based on the above-mentioned heat treatment definition, all of the examples 1 to 6 and comparative examples 1 to 3 and 5 (all of which have a Tg of 75°C) described below, except for example 2, had a heating temperature of 50°C after transverse stretching, which does not satisfy the above-mentioned temperature range, and therefore are not considered to be examples in which heat treatment according to the present invention was performed. In contrast, in example 2, the heating temperature after transverse stretching was 75°C, and therefore it is considered to be an example in which heat treatment according to the present invention was performed. The longer the heat treatment time, the easier it is to exhibit the effect, but if it is too long, the equipment will become large, so it is preferable to control it to between 1 and 9 seconds, and more preferably between 5 and 8 seconds. In the heat treatment step, the film can be relaxed in the width direction by reducing the distance between the holding clips in the tenter, which can prevent dimensional changes and deterioration of heat shrinkage properties after storage. [Example]

[0049] Next, the present invention will be specifically explained using examples and comparative examples, but the present invention is not limited to the aspects of these examples and can be modified within the scope of the present invention.

[0050] [Polyester synthesis] A stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser was charged with terephthalic acid (TPA), isophthalic acid (IPA), sebacic acid (SA), and adipic acid (AA) as acid components, and ethylene glycol (EG), neopentyl glycol (NPG), 1,4-cyclohexanedimethanol (CHDM), and butanediol (BD) as glycol components, so that the resin composition after polymerization would be as shown in Table 1. An esterification reaction was carried out over 4 hours at 140 to 220°C while removing the distilled water from the system. The pressure was then gradually reduced to 133.3 Pa over 60 minutes, and the temperature was raised to 270°C. A polycondensation reaction was then carried out at 270°C for approximately 90 minutes under reduced pressure of 13.3 to 40.0 Pa, yielding copolymer polyesters A to C. The resin compositions of the resulting copolymer polyesters A to G are shown in Table 1. Note that DEG in Table 1 stands for diethylene glycol, a by-product of the polymerization. In Table 1, the "Acid Components" column shows the content of each monomer component in 100 mol% of all acid components, and the "Polyhydric Alcohol Components" column shows the content of each monomer component in 100 mol% of all polyhydric alcohol components.

[0051] [Table 1]

[0052] [Manufacturing method of film 1] Polyester D and polyester E were mixed in a mass ratio of 95:5 and charged into an extruder. This mixed resin was melted at 280°C, extruded through a T-die, and quenched by being wound around a rotating metal roll cooled to a surface temperature of 30°C, yielding an unstretched film approximately 150 μm thick. The Tg of the unstretched film was 75°C. The resulting unstretched film was introduced into a transverse stretching machine (tenter) and preheated at 135°C for 5 seconds. After preheating, the film was continuously introduced into the first half of the transverse stretching zone and transversely stretched to 2.1 times at 105°C. It was then transversely stretched to 1.9 times at 81°C in the second half of the transverse stretching zone. The final transverse stretching ratio was 4.0 times. Finally, it was heat-treated in the heat treatment zone at 50°C for 3 seconds, cooled, and both edges were trimmed and removed. The film was then wound into a roll with a width of approximately 242 mm, continuously producing a transversely stretched film with a thickness of 40 μm over the specified length, yielding Film 1. The production conditions and properties of Film 1 are shown in Table 2.

[0053] [Manufacturing methods for films 2 to 6] Films 2 to 6 were produced and evaluated using the same production method as for Film 1, except that the polyester raw material and transverse stretching conditions were changed. The production conditions and properties of each film are shown in Table 2. For Film 6, the calculation method of the crystallinity using the above formula 3 cannot be applied, so the column in Table 2 is marked with "-".

[0054] [Shrinkage finish] From the roll of heat-shrinkable labels, heat-shrinkable labels were cut longitudinally at 90 mm intervals and collected. These labels were placed on commercially available 280 ml PET bottles (manufactured by Ito En Co., Ltd., Oi Ocha, filled, unopened), and then passed through steam using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc. to cause heat shrinkage (tunnel conditions are described in the Examples or Comparative Examples). The finish of the label after shrinkage was visually evaluated on a 5-point scale according to the following criteria: The defects described below include jumping up, wrinkles, insufficient shrinkage, folded-in label edges, whitening due to shrinkage, and fading of printing ink. 5: Best finish (no defects) 4: Good finish (one defect) 3: There are two flaws 2: 3 to 5 defects 1: Many defects (6 or more)

[0055] [Heat shrinkage rate (after heat shrinkage)] A sample measuring 4 mm lengthwise and 25 mm widthwise (around the bottle circumference) was cut from the label for which the shrinkage finish was evaluated, and the thermal shrinkage was measured in displacement mode using a Seiko Instruments TMA SS100. The sample was attached to a probe using a special chuck with a 15 mm chuck distance and the direction between the chucks aligned with the width of the label, and the temperature was raised from 30°C to 130°C at a rate of 10°C / min under a load of 49 mN. The thermal shrinkage was calculated from the obtained displacement using the following formula 1. Heat shrinkage rate (%) = {(length before shrinkage - length after shrinkage) / length before shrinkage} x 100 Formula 1

[0056] [Resin composition of base film] 10 mg of the substrate film with the printed layer removed from the package was dissolved in 0.6 ml of a solvent consisting of a 85% / 15% volume mixture of deuterated chloroform and trifluoroacetic acid, and 1H-NMR analysis was performed using a Varian Gemini-200 (500 MHz) nuclear magnetic resonance analyzer (NMR) with 32 accumulations. The resulting NMR spectrum was analyzed using JEOL RESONANCE software (JEOL), and the molar percentage of the resin was determined from the integral ratio. [Melting point (Tm), heat of fusion (ΔHm)] The melting point Tm and heat of fusion ΔHm were determined according to JIS-K7121-1987 using a differential scanning calorimeter (model: DSC220) manufactured by Seiko Electronics Co., Ltd. Specifically, 10 mg of the base film from which the printed layer had been removed was heated from 30°C to 300°C at a heating rate of 10°C / min, and an endothermic curve was measured. The peak temperature appearing at 140°C or higher on the obtained endothermic curve was taken as the melting point Tm (°C), and the area of ​​that peak was taken as the heat of fusion ΔHm (J / g). Note that when two or more endothermic peaks appeared, the peak with the highest temperature was taken as Tm, and ΔHm was determined from there.

[0057] [Heat-resistant blocking] The labeled bottles used to evaluate the shrinkage finish were filled with water and capped. Ten bottles were then placed in a thermostatic chamber (Espec LHU-124) adjusted to 60°C / 50%RH so that the labels were in contact with each other and left for one week. The labeled bottles were then removed, and heat blocking resistance was evaluated, with a score of ◯ if the labels were not blocking and an × if they were blocking.

[0058] [Recyclability] Five hundred labeled bottles used in the evaluation of shrinkage finish were crushed to obtain flakes, which were then washed with a 3.5 wt% sodium hydroxide solution at 85°C for 30 minutes with stirring at a flake concentration of 10 wt%. After the alkaline wash, the flakes were removed and washed with distilled water at 25°C for 20 minutes with stirring at a flake concentration of 10 wt%. This water wash was repeated two more times, each time replacing the distilled water. The washed flakes were dried, melted in an extruder, and filtered twice through successively smaller mesh filters to remove finer impurities, and finally through a filter with the smallest mesh size (50 μm) to obtain recycled polyester. Recycled polyester was also obtained from PET bottles without labels using the same method. Recyclability was evaluated based on the presence or absence of poor flake penetration and filter pressure buildup during polyester recycling. Compared to flakes without labels, flakes with labels were evaluated as ○ if they had the same number of times of poor penetration or filter pressure increase or one more time, and × if they had two or more times more. The following properties were evaluated for each of the polyester films shown in Table 2 below.

[0059] [Heat shrinkage rate (before heat shrinkage)] The polyester film was cut into a 10 cm x 10 cm square and immersed in hot water at a specified temperature [(90°C or 70°C) ± 0.5°C] for 10 seconds without load to allow it to shrink, then immersed in water at 25°C ± 0.5°C for 10 seconds and pulled out of the water, and the dimensions of the film in the longitudinal and transverse directions were measured, and the thermal shrinkage rate for each direction was calculated according to the following formula 1. The direction with the largest thermal shrinkage rate was defined as the main shrinkage direction (width direction). Heat shrinkage rate (%) = {(length before shrinkage - length after shrinkage) / length before shrinkage} x 100 Formula 1

[0060] [Thickness unevenness in the width direction (before heat shrinkage)] A wide strip of film measuring 40 mm in the longitudinal direction and 1.2 m in the width direction was sampled from the film roll, and the thickness was measured continuously across the width of the film sample (measurement length: 1 m) at a measurement speed of 5 m / min using a continuous contact thickness meter manufactured by Micron Measuring Instruments Co., Ltd. The maximum thickness during measurement was defined as Tmax., the minimum thickness as Tmin., and the average thickness as Tave. The thickness unevenness across the width of the film was calculated according to the following formula 2. Thickness unevenness (%) = {(Tmax. - Tmin.) / Tave.} × 100 Equation 2

[0061] [Maximum heat shrinkage stress in width direction (before heat shrinkage)] A sample measuring 4 mm in the longitudinal direction and 25 mm in the transverse direction was cut out from the polyester film, and the maximum thermal shrinkage stress was measured in stress mode using a TMA SS100 manufactured by Seiko Electronics Industries, Inc. The sample was attached to the probe using a special chuck with a 15 mm distance between the chucks so that the direction between the chucks was the transverse direction of the film, and the temperature was raised from 30°C to 130°C at a rate of 10°C / min with an initial load of 40 mN. The maximum value of the shrinkage stresses measured was taken as the maximum shrinkage stress in the transverse direction.

[0062] [Haze (before heat shrinkage)] Measurement was carried out in accordance with JIS K7136 using a haze meter "500A" (manufactured by Nippon Denshoku Industries Co., Ltd.) The measurement was carried out twice, and the average value was calculated.

[0063] [Crystallization (before heat shrinkage)] The density d of a sample of approximately 3 mm square was measured using an aqueous calcium nitrate solution according to the density gradient tube method of JIS-K-7112, and the crystallinity was measured according to the following formula 3. Crystallinity (%)={dc×(d-da) / (d×(dc-da)}×100 Formula 3 dc:1.455g / cm 3 (Density of perfectly crystalline polyethylene terephthalate) da: 1.335 g / cm 3 (Density of completely amorphous polyethylene terephthalate) d: density of sample (g / cm 3 )

[0064] [Tg: Glass transition temperature (before heat shrinkage)] Tg was determined according to JIS-K7121-1987 using a differential scanning calorimeter (model: DSC220) manufactured by Seiko Instruments Inc. Specifically, 10 mg of unstretched film was heated from -40°C to 120°C at a heating rate of 10°C / min, and an endothermic curve was measured. Tangent lines were drawn before and after the inflection point of the obtained endothermic curve, and the intersection point was defined as the glass transition point (Tg; °C).

[0065] Using the polyester raw materials D to G, various polyester films listed in Table 2 were obtained.

[0066] [Table 2]

[0067] [Example 1] The entire surface of Film 1, except for 20 mm from the edge in the width direction of the roll, was repeatedly printed for labels (three-color printing) using grass, gold, and white inks manufactured by Toyo Ink Co., Ltd., and then wound up to produce a printed film roll. The printed film was unwound from this roll, and an adhesive solvent composition made by mixing 1,3-dioxolane / polyester A in a weight ratio of 90 / 10 was applied to the inside of one edge in the film width direction in a coating width of 4±2 mm at 300 mg / m². 2The solvent composition was adjusted to be equal to or less than 1000 kJ / min, and the solvent composition was continuously applied at a processing speed of 400 m / min. The film was folded and adhered to the other widthwise end of the film, with the overlapping portion at the center, to produce a label (a label with the main shrinkage direction of the heat-shrinkable film as the circumferential direction) using the heat-shrinkable film as a ring. Thereafter, two parallel perforations (perforations with holes of about 1 mm diameter spaced about 4 mm apart) were formed in the longitudinal direction of the label at intervals of about 22 mm, and the label was continuously wound up. The heat-shrinkable label was then wound into a roll and passed through a steam tunnel to be heat-shrunk. The tunnel was divided into three zones, with the temperatures in zones 1, 2, and 3 set to 60, 79, and 81°C, respectively, and the total residence time in all zones was set to 28 seconds. The production conditions and the obtained properties of Example 1 are shown in Table 3, and the thermal shrinkage obtained by TMA is shown in FIG.

[0068] [Examples 2 to 7, Comparative Examples 1 to 4] Packages of Examples 2 to 7 and Comparative Examples 1 to 4 were produced in the same manner as in Example 1 above, except that the film, adhesive solvent composition, steam tunnel temperature and residence time used in Example 1 were changed as shown in Table 3. The production conditions and the obtained properties of Example 1 are shown in Table 3. For Comparative Example 1, the thermal shrinkage obtained by TMA is shown in FIG.

[0069] [Table 3]

[0070] The packages of Examples 1 to 7, which satisfied the requirements of the present invention, had a beautiful appearance with a shrinkage finish rating of 4 or 5, and the adhesive strength, residual shrinkage rate, melting point, heat blocking resistance, and recyclability of the packages also fell within the specified ranges, making them preferable. In contrast, in Comparative Example 1, Film 5 was used, which had a low thermal shrinkage rate of 26.8% in the width direction at 90°C, so the peak residual thermal shrinkage rate of the package did not appear below 120°C (residual shrinkage rate at 120°C was 0.9%), and the shrink finish of the package was significantly reduced (Evaluation 1). Therefore, the heat blocking resistance test and recyclability were not evaluated.

[0071] In Comparative Example 2, Film 7 was used, which had a thickness variation of 22.0% in the width direction, so the ink on the packaging was not printed evenly, resulting in many defects such as fading, and therefore poor shrinkage finish (Evaluation 2). In addition, because Film 7 used amorphous materials (Polyesters F and G), the melting point was low at 173°C, and the heat of fusion (ΔHm) was also reduced to 17 J / g, resulting in the evaluation of heat blocking resistance and recyclability being "poor."

[0072] In Comparative Example 3, the adhesive solvent was 1,3-dioxolane alone, which resulted in zero adhesive strength (no adhesion), making it impossible to produce a circular package. Therefore, the heat-resistant blocking test and recyclability were not evaluated. In Comparative Example 4, the residual shrinkage rate after heat shrinkage was as high as 44.9%, and the shrink finish was significantly reduced (Evaluation 1). [Industrial Applicability]

[0073] As described above, the packaging of the present invention has excellent adhesive strength and shrink finish, and since it is made from a raw material consisting essentially of polyethylene terephthalate, it can be recycled together with PET bottles. Therefore, the present invention is useful as a packaging for beverage bottles.

Claims

1. A packaging body in which a ring-shaped body having a printed portion and a heat-shrinkable polyester film as a base material and both ends of the film adhered thereto is heat-shrunk and covers at least a part of the outer periphery of a PET bottle, the packaging body being characterized in that the covered ring-shaped body satisfies the following requirements (1) to (3): (1) The heat-shrinkable polyester film as the substrate is composed of at least one selected from the group consisting of wax, antioxidant, antistatic agent, crystal nucleating agent, viscosity reducer, heat stabilizer, coloring pigment, coloring inhibitor, ultraviolet absorber, and fine particles, and polyester, wherein the polyester is composed of 100 mol % of ethylene terephthalate units or 90 mol % or more of ethylene terephthalate units and an amorphous monomer component, the amorphous monomer component being composed of an amorphous acid monomer component and / or an amorphous alcohol monomer component, and the amorphous acid monomer component is composed of an ethylene terephthalate unit and / or an amorphous alcohol monomer component. The amorphous alcohol monomer component is at least one selected from the group consisting of phthalic acid, 1,4-cyclohexanedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid, and the amorphous alcohol monomer component is at least one selected from the group consisting of neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, and hexanediol. (2) The heat-shrinkable polyester film used as the base material has a melting peak during the temperature rise process in a differential scanning calorimeter (DSC), and the melting point (Tm) of the peak temperature is 200°C or higher and 280°C or lower, and the heat of fusion (ΔHm) of the peak area is 40 J / g or higher and 60 J / g or lower. (3) In the circumferential direction of the object to be packaged, the peak of the heat shrinkage rate of the heat-shrinkable polyester film serving as the base material, as determined by thermomechanical analysis (TMA), appears at 60°C or higher and 120°C or lower, and the heat shrinkage rate at the peak is 1% or higher and 40% or lower.

2. 2. The package according to claim 1, wherein the peel strength of the adhesive portion of the coated annular body is 2 N / 15 mm or more and 15 N / 15 mm or less.

3. 3. The package according to claim 1, wherein the heat-shrinkable polyester film serving as the base material has an intrinsic viscosity (IV) of 0.5 dL / g or more and 0.8 dL / g or less.

4. 4. The package according to claim 1, wherein the adhesion is achieved by an organic solvent composition.

5. 5. The package according to claim 4, wherein the organic solvent composition contains a polymer component.

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