Heat-shrinkable label and method of producing container with label

Abstract

A heat-shrinkable label (1) is suitable for being tightly affixed to a container (4) and attached to the container (4) by heat shrinkage resulting from steam being sprayed onto said label. The heat-shrinkable label (1) satisfies requirements (1) to (4) and comprises: a multilayer film in which a first polyester resin layer, a polystyrene resin layer, and a second polyester resin layer have been stacked in the stated order; or a polyester resin film.　(1) The widthwise shrinkage ratio after 10 seconds of immersion in a 60°C hot water bath is 1% or less.　(2) The widthwise shrinkage ratio after 10 seconds of immersion in a 70°C hot water bath is 10% or less.　(3) The widthwise shrinkage ratio after 10 seconds of immersion in a 90°C hot water bath is 40% or more.　(4) The widthwise shrinkage ratio after 7 days of storage in an atmosphere at a temperature of 55°C or after 1 day of storage in an atmosphere at a temperature of 55°C and humidity of 30%, followed by 6 days of storage in an atmosphere at a temperature of 40°C and humidity of 90% is 0.5% or less.

Description

Method for manufacturing heat-shrinkable labels and labeled containers

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to methods for making heat-shrinkable labels and labeled containers.

[0002] For example, heat-shrinkable films used in heat-shrinkable labels that are heat-shrunk and attached to the outer surface of containers such as PET bottles for product labeling, etc., have heat-shrinkability such that they hardly shrink naturally at room temperature but shrink rapidly when heated to 60°C or higher.

[0003] However, in seasons when the outside temperature rises, the ambient temperature in warehouses, truck beds, etc. can rise to nearly 50°C, which approaches the shrinkage initiation temperature of heat-shrinkable films. Therefore, heat-shrinkable films and heat-shrinkable labels need to be kept refrigerated during storage and transportation.

[0004] To solve these problems, for example, Patent Document 1 describes a heat-shrinkable polyester film that does not shrink (so-called natural shrinkage) even when stored in an outdoor warehouse without temperature control during high summer temperatures, that shows only a small decrease in the shrinkage rate in the main shrinkage direction of the heat-shrinkable film, and that can be beautifully and efficiently attached to containers such as PET bottles as labels without changing the temperature conditions for heat shrinkage when heat-shrinking and attaching the film to the container.

[0005] WO2011 / 114934 publication

[0006] A cylindrical label is produced from the heat-shrinkable polyester film described in Patent Document 1, with the main shrinkage direction of the heat-shrinkable polyester film being the circumferential direction, and the label is thermally shrunk by passing through a hot air tunnel with a zone temperature of 150°C for 10 seconds. When the label is attached to a PET bottle, it is said to have good finish (paragraphs

[0090] and

[0111] of Patent Document 1).

[0007] When attaching a heat-shrinkable label to a container such as a PET bottle filled with a low-temperature liquid by heat shrinking it, it is necessary to use a steam tunnel that can heat-shrink the heat-shrinkable label even when the container surface is at a low temperature. However, when a container such as a PET bottle fitted with a heat-shrinkable label made of a heat-shrinkable polyester film as described in Patent Document 1 is passed through a steam tunnel, the heating temperature is lower (100°C or lower) than in a hot air tunnel, which poses a problem of poor finish due to insufficient heat shrinkage of the heat-shrinkable label.

[0008] According to the present disclosure, it is possible to provide a heat-shrinkable label that is suitable for being attached to a container by being thermally shrunk by blowing steam onto the label, and that includes a multilayer film or a polyester-based resin film in which a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer are laminated in this order, and that satisfies the following requirements (1) to (4):

[0009] (1) The shrinkage rate in the width direction after immersion in a warm water bath at 60°C for 10 seconds is 1% or less.

[0010] (2) The shrinkage rate in the width direction after immersion in a warm water bath at 70°C for 10 seconds is 10% or less.

[0011] (3) The shrinkage rate in the width direction after immersion in a warm water bath at 90°C for 10 seconds is 40% or more.

[0012] (4) The shrinkage rate in the width direction is 0.5% or less after storage in an atmosphere at a temperature of 55°C for 7 days, or after storage in an atmosphere at a temperature of 55°C and humidity of 30% for 1 day and then storage in an atmosphere at a temperature of 40°C and humidity of 90% for 6 days.

[0013] According to the present disclosure, a method for manufacturing a labeled container can be provided, which includes the steps of placing the above-mentioned heat-shrinkable label so that it surrounds the outer peripheral surface of the container, and blowing steam onto the heat-shrinkable label to tightly adhere the heat-shrinked heat-shrinkable label to the outer peripheral surface of the container.

[0014] According to the present disclosure, it is possible to provide a heat-shrinkable label and a method for manufacturing a labeled container that can keep the natural shrinkage rate in the main shrinkage direction low even when stored in a high-temperature atmosphere such as 55°C, or when stored for one day in an atmosphere at a temperature of 55°C and a humidity of 30%, and then stored for six days in an atmosphere at a temperature of 40°C and a humidity of 90%, and that can improve the finish after being attached to a container by heating using steam.

[0015] Fig. 3 is a schematic plan view of an example of a heat-shrinkable film used in the manufacture of an example of a heat-shrinkable label of an embodiment. Fig. 4 is a schematic perspective view of an example of a heat-shrinkable label of an embodiment. Fig. 5 is a schematic perspective view illustrating an example of a process for installing a heat-shrinkable label of an embodiment so as to surround the outer peripheral surface of a container. Fig. 6 is a schematic cross-sectional view of an example taken along IV-IV in Fig. 3. Fig. 7 is a schematic plan view of an example of a labeled container of an embodiment.

[0016] Hereinafter, embodiments will be described. In the drawings used to describe the embodiments, the same reference numerals denote the same or corresponding parts.

[0017] <Heat-shrinkable Label> FIG. 1 shows a schematic plan view of an example of a heat-shrinkable film used in the manufacture of an example of a heat-shrinkable label of an embodiment. FIG. 2 shows a schematic perspective view of an example of a heat-shrinkable label of an embodiment. The heat-shrinkable film 10 shown in FIG. 1 shows a state before the heat-shrinkable label 1 of the embodiment shown in FIG. 2 is processed into a cylindrical shape. The heat-shrinkable label 1 of the embodiment shown in FIG. 2 can be produced, for example, by forming a continuous, long heat-shrinkable film 10 shown in FIG. 1 into a cylindrical shape and then cutting it into individual heat-shrinkable labels 1. The heat-shrinkable label 1 of the embodiment shown in FIG. 2 is a heat-shrinkable label suitable for being attached to a container by being thermally shrunk by blowing steam onto it. The heat-shrinkable label 1 includes a multilayer film or a polyester-based resin film formed by laminating a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer in this order, and satisfies the following requirements (1) to (4). (1) The shrinkage rate in the width direction when immersed in a 60°C warm water bath for 10 seconds is 1% or less. (2) The shrinkage rate in the width direction when immersed in a 70°C warm water bath for 10 seconds is 10% or less. (3) The shrinkage rate in the width direction when immersed in a 90°C warm water bath for 10 seconds is 40% or more. (4) The shrinkage rate in the width direction is 0.5% or less after storage in an atmosphere at a temperature of 55°C for 7 days or after storage in an atmosphere at a temperature of 55°C and 30% humidity for 1 day and then storage in an atmosphere at a temperature of 40°C and 90% humidity for 6 days.

[0018] 1 and 2, reference numeral 2 indicates the non-shrink direction (hereinafter referred to as the "longitudinal direction") of the heat-shrinkable film 10 and the heat-shrinkable label 1, respectively, and reference numeral 3 indicates the main shrink direction (hereinafter referred to as the "transverse direction") of the heat-shrinkable film 10 and the heat-shrinkable label 1, respectively. In this specification, the non-shrinkable direction (longitudinal direction 2) means a direction in which the shrinkage rate is smaller than that of the main shrinkage direction (transverse direction 3), and does not necessarily mean that there is no shrinkage at all. The angle between the longitudinal direction 2 and the transverse direction 3 of the heat-shrinkable film 10 and the heat-shrinkable label 1, respectively, is 90°.

[0019] As a result of extensive research, the present inventors have found that a heat-shrinkable label 1 containing the above-mentioned multilayer film or polyester-based resin film and satisfying the above-mentioned requirements (1) to (4) can maintain a low natural shrinkage rate in the width direction (the heat shrinkage rate when the heat-shrinkable label 1 is naturally heat-shrunk without being artificially heat-shrunk) even when stored for a long period of 7 days in a high-temperature atmosphere of, for example, 55°C, or when stored for 1 day in an atmosphere at a temperature of 55°C and a humidity of 30%, followed by storage for 6 days in an atmosphere at a temperature of 40°C and a humidity of 90%, and can also achieve high finish quality after attachment to a container by heating with steam, thereby completing the present invention.

[0020] From the viewpoint of improving the finish quality after attachment to a container by heating with steam, it is preferable that the heat-shrinkable label 1 further satisfy the following requirement (5): (5) The shrinkage rate in the width direction when immersed in a warm water bath at 80°C for 10 seconds is more than 10% and not more than 50% (more preferably more than 15% and not more than 50%).

[0021] The widthwise shrinkage percentage of the heat-shrinkable label 1 meeting the above requirements (1) to (3) and (5) is calculated by the following formula A from the widthwise lengths of the heat-shrinkable label 1 before and after immersion in a hot water bath heated to a temperature of 60°C to 90°C for 10 seconds under no load, after which the heat-shrinkable film 10 is processed into a cylindrical shape to form individual heat-shrinkable labels 1 and then continuously stored in an atmosphere at a temperature of 25°C or less. Note that before becoming the heat-shrinkable label 1, the heat-shrinkable film 10 may be exposed to an atmosphere exceeding 25°C for a short period of time, such as a few seconds to a few minutes, during transportation or storage reloading after production or during the moment when the print is dried before being processed into the heat-shrinkable label 1, but the heat-shrinkable label 1 is maintained at a temperature of 25°C or less without heat shrinkage.

[0022] Width direction shrinkage rate [%]=100×[{(width direction length of heat-shrinkable label 1 before immersion)−(width direction length of heat-shrinkable label 1 after immersion)} / (width direction length of heat-shrinkable label 1 before immersion)] (Equation A)

[0023] The widthwise shrinkage percentage of the heat-shrinkable label 1, as required by requirement (4), is calculated as follows: After the heat-shrinkable film 10 is manufactured, the heat-shrinkable film 10 is processed into a cylindrical shape to form individual heat-shrinkable labels 1, which are then continuously stored in an atmosphere at a temperature of 25°C or less, and the heat-shrinkable labels 1 are then stored in an atmosphere at a temperature of 55°C (humidity 1% to 2%) for 7 days (hereinafter, "storing in an atmosphere at a temperature of 55°C (humidity 1% to 2%) for 7 days" is also referred to simply as "aging"), or after being stored in an atmosphere at a temperature of 55°C and humidity 30% for 1 day and then stored in an atmosphere at a temperature of 40°C and humidity 90% for 6 days (hereinafter, also referred to as "humid aging"), the widthwise shrinkage percentage is calculated from the widthwise lengths of the heat-shrinkable labels 1 before and after storage using the following formula (B):

[0024] Width direction shrinkage rate [%]=100×[{(width direction length of heat shrinkable label 1 before aging or humidity aging)−(width direction length of heat shrinkable label 1 after aging or humidity aging)} / (width direction length of heat shrinkable label 1 before aging or humidity aging)] (Equation B)

[0025] Furthermore, it is preferable that the heat-shrinkable label 1 satisfies at least the above requirements (1) to (3) and (5) both before and after the aging process and both before and after the humidification aging process. In this case, the natural shrinkage rate in the width direction can be kept low even when the label is stored in a high-temperature atmosphere such as 55°C, or when the label is stored in an atmosphere at a temperature of 55°C and 30% humidity for one day and then in an atmosphere at a temperature of 40°C and 90% humidity for six days, and the finish quality after attachment to a container by heating with steam can be improved.

[0026] The widthwise shrinkage percentage of the heat-shrinkable label 1 before the aging or humidity aging, which satisfies the requirements (1) to (3) and (5), is calculated by the above formula A. The widthwise shrinkage percentage of the heat-shrinkable label 1 after the aging or humidity aging, which satisfies the requirements (1) to (3) and (5), is calculated as follows: The heat-shrinkable label 1 after the aging or humidity aging is immersed in a warm water bath heated to a temperature of 60°C to 90°C for 10 seconds under no load, and the widthwise shrinkage percentage is calculated from the widthwise lengths of the heat-shrinkable label 1 before and after immersion, using the following formula C:

[0027] Width direction shrinkage rate [%]=100×[{(width direction length of heat-shrinkable label 1 after the aging or humidification aging before immersion)−(width direction length of heat-shrinkable label 1 after the aging or humidification aging after immersion)} / (width direction length of heat-shrinkable label 1 after the aging or humidification aging before immersion)] (Equation C)

[0028] <Method for Manufacturing Heat-Shrinkable Label> The heat-shrinkable label 1 of this embodiment can be manufactured, for example, as follows. First, a polyester-based resin raw material and a polystyrene-based resin raw material are prepared to manufacture the heat-shrinkable film 10. The polyester-based resin raw material can be, for example, a resin containing 50 mol% or more of ethylene terephthalate units and containing an amorphous component modified with other glycol components such as 1,4-cyclohexanedimethanol or neopentyl glycol, or other dicarboxylic acid components such as isophthalic acid. The polystyrene-based resin raw material can be, for example, a styrene-based resin such as a styrene-butadiene copolymer resin, which is likely to provide gradual heat shrinkability in the heat-shrinkable film 10.

[0029] Next, an unstretched multilayer film is produced using the polyester-based resin raw material and the polystyrene-based resin raw material, or an unstretched polyester-based resin film is produced using the polyester-based resin raw material.

[0030] An unstretched multilayer film can be produced, for example, as follows. First, the polyester-based resin raw material and the polystyrene-based resin raw material are fed into an extruder. Next, the raw material is extruded through a multilayer die into a three-layer sheet having a polystyrene-based resin layer between two polyester-based resin layers (a first polyester-based resin layer and a second polyester-based resin layer). The extruded three-layer sheet is then cooled and solidified. This allows the production of an unstretched multilayer film. The multilayer film is not limited to a three-layer structure. For example, a five-layer structure, a six-layer structure, or a seven-layer structure having another resin layer (e.g., a mixed resin of a polyester-based resin and a polystyrene-based resin, or a resin layer containing other resin components, adhesive components, etc.) between the polyester-based resin layer and the polystyrene-based resin layer can also be used. Furthermore, an unstretched polyester-based resin film can be produced in the same manner as an unstretched multilayer film, except that the polyester-based resin raw material is extruded into a single layer or multiple layers. As an unstretched film of a multilayer polyester-based resin film, for example, a laminate of three polyester-based resin layers of different types (where the middle polyester-based resin layer and the polyester-based resin layers on both sides have different amorphous components in terms of their presence or ratio, or where recycled PET is laminated onto the middle polyester-based resin layer) can be used.

[0031] The unstretched film can be produced by a conventional method such as melt film formation, but the melt film formation method (particularly the T-die method) is preferably used as the method for producing the unstretched film. Furthermore, the resin lamination method can be a conventional method such as co-extrusion (feed block method, multi-manifold method, etc.), with the feed block method being preferred.

[0032] A specific example of the co-extrusion method (feed block method) is a method in which raw materials (polystyrene-based resin layer) forming the intermediate portion and raw materials (polyester-based resin layer) forming the surface portion are respectively fed into multiple extruders set at predetermined temperatures, and then co-extruded through a T-die using a feed block in a predetermined layered configuration. The extrusion temperature varies depending on the type of resin used and is not particularly limited, but is preferably, for example, about 150 to 250°C. An unstretched film (sheet) can be produced by contacting the polymer co-extruded through the T-die with a cooling drum and quenching it.

[0033] Next, the unstretched film produced as described above is stretched to impart heat shrinkability, thereby producing a heat-shrinkable film 10. The stretching can be performed by biaxial stretching in the longitudinal direction 2 and the width direction 3, or uniaxial stretching in the width direction 3. As the stretching method, for example, any of a roll method, a tenter method, and a tube method can be used. Furthermore, when performing the stretching by biaxial stretching in the longitudinal direction 2 and the width direction 3, the film may be stretched biaxially simultaneously or sequentially.

[0034] A specific example of stretching processing is a method in which the unstretched film prepared as described above is introduced into a longitudinal stretching device and then introduced into a transverse stretching device. More specifically, for example, the film can be stretched in the longitudinal direction 2 by roll-type longitudinal stretching at a stretching temperature of 65 to 100°C and a stretching ratio of 1.05 to 1.50, and then stretched in the width direction 3 by tenter-type transverse stretching at a stretching temperature of 70 to 120°C and a stretching ratio of 3 to 8 (preferably 4 to 7). After stretching in the width direction 3, the film can be subjected to heat treatment (heat setting at a temperature lower than the stretching temperature) while clipped by a tenter, or a relaxation heat treatment in which the tenter is slightly relaxed. The stretching processing can also be performed in multiple stages, and heat treatments such as annealing can also be performed. In particular, the heat shrinkage rate of the heat-shrinkable film 10 (heat-shrinkable label 1) at each temperature and the natural shrinkage rate during storage can be adjusted by the stretching temperature, stretching ratio, and temperature and time of heat treatment during the stretching process.

[0035] After the unstretched film is stretched as described above, it is wound up on a roll and slit (cut) to a predetermined width, thereby producing the heat-shrinkable film 10 wound up in a roll of a predetermined width.

[0036] Next, the heat-shrinkable film 10 is unwound from the roll of heat-shrinkable film 10 prepared as described above, and various characters, designs, etc. are printed or various coatings are applied to the surface of the heat-shrinkable film 10 by a printing method such as gravure printing or flexographic printing, and then the heat-shrinkable film 10 is slit to cut to a predetermined width according to the label dimensions, and then rewound into a roll.

[0037] Next, the heat-shrinkable film 10 is unwound from the slit roll, both edges in the width direction 3 are joined (envelope-sealed) with an adhesive or the like to form a cylindrical bag, which is then folded flat and wound up into a roll, thereby producing a long label roll product in which the heat-shrinkable labels 1 are connected in the vertical direction 2. Note that the heat-shrinkable label 1 may be provided with perforations in the vertical direction or the like for label removal during the processing.

[0038] By going through the above steps, it is possible to produce the heat-shrinkable label 1 of the embodiment that satisfies the above requirements (1) to (4), preferably the above requirements (1) to (5).

[0039] <Method for manufacturing labeled container> An example of a method for manufacturing a labeled container of the embodiment will now be described with reference to Figures 2 to 4. First, as shown in the schematic perspective view of Figure 2, a step of producing a single heat-shrinkable label 1 of the embodiment is performed. This step can be performed, for example, by cutting a long heat-shrinkable label 1 that has been made into a cylindrical shape and folded so as to surround an imaginary axis 2' extending along the longitudinal direction 2 into single heat-shrinkable labels 1, and then unfolding the folded label 1 into a cylindrical shape (approximately cylindrical).

[0040] Next, as shown in the schematic perspective view of Figure 3, a step of installing a heat-shrinkable label 1 so that it surrounds the outer peripheral surface of the container is performed. This step can be performed, for example, by fitting the tubular heat-shrinkable label 1 onto the container 4 so that the inner peripheral surface 1a of the label 1 surrounds the outer peripheral surface 40 of the container 4. Here, the outer peripheral surface 40 of the container 4 has a body portion 41 located at the bottom of the container 4, a shoulder portion 42 located above the body portion 41, and a mouth portion 43 located above the shoulder portion 40. The heat-shrinkable label 1 can be installed, for example, by fitting from the body portion 41 to the shoulder portion 40 of the outer peripheral surface 40 of the container 4.

[0041] Figure 4 shows a schematic cross-sectional view of an example taken along line IV-IV in Figure 3. The heat-shrinkable label 1 is preferably placed so as to surround the outer peripheral surface 40 of the container 4 such that the circumferential length of the inner peripheral surface 1a of the heat-shrinkable label 1 is 15 mm to 30 mm longer than the circumferential length of the outer peripheral surface 40 of the container 4. In particular, when the circumferential length of the outer peripheral surface 40 of the container 4 is, for example, 180 mm to 250 mm, it is more preferable that the heat-shrinkable label 1 be placed so as to surround the outer peripheral surface 40 of the container 4 such that the circumferential length of the inner peripheral surface 1a of the heat-shrinkable label 1 is 18 mm to 26 mm longer than the circumferential length of the outer peripheral surface 40 of the container 4. A margin is necessary to ensure machine-readable attachment of the heat-shrinkable label 1 to the container 4 (i.e., the label 1 can be cut from a folded, long sheet of heat-shrinkable label 1 into individual labels, opened, and fitted to the container 4 at a high speed of, for example, 200 labels per minute or more). However, natural shrinkage of the heat-shrinkable label 1 reduces the margin, and wrinkles or distortions in the heat-shrinkable label 1 prior to fitting tend to impair attachment to the container 4. Setting the circumferential length as described above can improve the finished appearance of the heat-shrinkable label 1 after heat shrinkage and fitting to the container 4. While FIG. 4 illustrates a case in which the outer peripheral surface 40 of the container 4 and the inner peripheral surface 1a of the heat-shrinkable label 1 have circular cross-sectional shapes, the cross-sectional shape of the container is not limited to a circular shape and may be polygonal, such as a square, or may have circular and polygonal or uneven portions. The heat-shrinkable label 1 may also be cylindrical, with two to four creases remaining when folded flat.

[0042] Next, a step is performed in which steam is blown onto the heat-shrinkable label 1 to adhere the heat-shrunk heat-shrinkable label 1 to the outer surface 40 of the container 4. This step can be performed, for example, by passing the container 4 fitted with the heat-shrinkable label 1 through a steam tunnel and blowing steam onto the entire heat-shrinkable label 1 in the atmospheric pressure steam tunnel. However, from the viewpoint of improving the finish of the heat-shrinkable label 1 attached to the container 4, it is preferable to perform this step by a process including a step of blowing first steam 51 onto a first portion of the heat-shrinkable label 1 located below the outer surface 40 of the container 4 and, after the step of blowing first steam 51, a step of blowing second steam 52 onto a second portion of the heat-shrinkable label 1 located above the outer surface 40 of the container 4. Furthermore, from the viewpoint of improving the finish quality when the heat-shrinkable label 1 is attached to the container 4, it is even more preferable to include a step of spraying third steam onto a third portion between the first and second portions of the outer surface 40 of the container 4 between the step of spraying first steam 51 and the step of spraying second steam 52. The steam (including the first steam 51, the second steam 52, and the third steam) sprayed onto the heat-shrinkable label 1 can be, for example, water vapor (a mixture of saturated water vapor and steam formed by condensation of water vapor) generated in a boiler and at a temperature of 100°C or less, preferably 80°C to 90°C.

[0043] The labeled container of the embodiment can be manufactured through the above steps. Figure 5 shows a schematic plan view of an example of a labeled container of the embodiment. In the labeled container 50 of the embodiment shown in Figure 5, the heat-shrinkable label 1 after heat shrinkage is in close contact with the outer peripheral surface 40 of the container 4, and the heat-shrinkable label 1 after heat shrinkage is attached to the outer surface 40 of the container 4 from the body portion 41 to the shoulder portion 40.

[0044] <Effects> The heat-shrinkable label 1 of the embodiment satisfies the above requirements (1) to (4), preferably requirements (1) to (5). Therefore, even when stored in a high-temperature atmosphere such as 55°C, or when stored for one day in an atmosphere at a temperature of 55°C and 30% humidity followed by six days in an atmosphere at a temperature of 40°C and 90% humidity, the heat-shrinkable label 1 can maintain a low natural shrinkage rate in the width direction and achieve a good finish after being attached to a container by heating with steam. Therefore, even when the heat-shrinkable label 1 of the embodiment is actually transported from a manufacturing plant for the heat-shrinkable label 1 to a beverage or other product factory where the heat-shrinkable label 1 is used, or when stored in a warehouse (for seven days or more), or when transported by truck for one day at a temperature of 55°C and 30% humidity and then stored in a warehouse for six days at a temperature of 40°C and 90% humidity, the heat-shrinkable label 1 is resistant to dimensional changes and wrinkles due to shrinkage and remains usable even at high temperatures of 50°C to 55°C. Therefore, it does not require refrigerated storage at or below 25°C, is easy to handle, and reduces the energy required for refrigeration. Furthermore, when the heat-shrinkable label 1 after the aging or humidification aging is immersed in an 80°C hot water bath for 10 seconds, the widthwise shrinkage is preferably greater than 10%, and when the heat-shrinkable label 1 before and after the aging or humidification aging is immersed in an 80°C hot water bath for 10 seconds, the decrease in widthwise shrinkage is preferably 15% or less, and more preferably 10% or less. When the decrease is 15% or less, particularly 10% or less, good shrinkage can be obtained in either state. The decrease in widthwise shrinkage when the heat-shrinkable label 1 before and after the aging or humidification aging is immersed in an 80°C hot water bath for 10 seconds can be calculated using the following formula (D). Because the heating temperature of the heat-shrinkable label 1 when sprayed with steam is typically 80°C to 90°C, it is important that the decrease in widthwise shrinkage when the heat-shrinkable label 1 is immersed in an 80°C hot water bath for 10 seconds is small.

[0045] Decrease in widthwise shrinkage percentage [%] = (measured value of widthwise shrinkage percentage when the heat-shrinkable label 1 before the aging or the humidification aging is immersed in a hot water bath at 80°C for 10 seconds) - (measured value of widthwise shrinkage percentage when the heat-shrinkable label 1 after the aging or the humidification aging is immersed in a hot water bath at 80°C for 10 seconds) (Equation D)

[0046] In particular, the heat-shrinkable label 1 of the embodiment is preferably such that the required shrinkage rate (the required shrinkage rate at the maximum shrinkage position) at the uppermost end of the shoulder portion 42 of the outer peripheral surface 40 of the container 4 is 40% or more and 50% or less, from the viewpoint of improving the finish quality after attachment to the container 4. The heat-shrinkable label 1 of the embodiment can keep the natural shrinkage rate in the width direction low even when stored for a long period of time, such as 7 days, in a high-temperature atmosphere at 55°C or when stored for 1 day in an atmosphere at a temperature of 55°C and a humidity of 30%, and then stored for 6 days in an atmosphere at a temperature of 40°C and a humidity of 90%. Therefore, even when the label naturally shrinks during storage in such an atmosphere, it can be attached to a portion requiring a high shrinkage rate, such as the shoulder portion 42 of the outer peripheral surface 40 of the container 4. In addition, a required shrinkage rate of 40% or more and 50% or less means that when the circumference of the inner surface 1a of the heat-shrinkable label 1 before heat shrinkage by spraying steam is 100%, the reduction rate of the circumference of the inner surface 1a of the heat-shrinkable label 1 after heat shrinkage by spraying steam is 40% or more and 45% or less.

[0047] The body portion 41 of the outer peripheral surface 40 of the container 4 can be a portion of the container 4 where the variation in the cross-sectional area of ​​the container 4 is relatively small from the lowermost end of the container 4 upward, for example, as shown in FIG. 4. The shoulder portion 42 of the outer peripheral surface 40 of the container 4 can be a portion of the container 4 where the cross-sectional area of ​​the container 4 decreases from the upper end of the body portion 41 of the container 4 upward, for example, as shown in FIG. 4 (i.e., the shoulder portion 42 has a smaller diameter portion than the body portion 41). The mouth portion 43 of the outer peripheral surface 40 of the container 4 can be a portion of the container 4 where the variation in the cross-sectional area of ​​the container 4 is relatively small from the upper end of the shoulder portion 42 of the container 4 upward, for example, as shown in FIG. Experimental example

[0048] By appropriately changing the manufacturing conditions, etc., several types of heat-shrinkable film with various widthwise shrinkage rates were prepared, and each of the prepared heat-shrinkable films was printed with a letter pattern and solid white, slit to a specified width, and then center-sealed (bag-making process) to produce long, tubular heat-shrinkable labels of Experimental Examples 1 to 8.

[0049] The heat-shrinkable labels of Experimental Examples 1 to 3 and 6 were each made of a 35 μm-thick multilayer film in which a first polyester-based resin layer, a polystyrene-based resin layer, and a second polyester-based resin layer were laminated in that order. The heat-shrinkable labels of Experimental Examples 4, 7 and 8 were made of a 20 μm-thick polyester-based resin film. The heat-shrinkable label of Experimental Example 5 was made of a 30 μm-thick polyester-based resin film.

[0050] <Width-direction shrinkage ratio of heat-shrinkable labels of Experimental Examples 1 to 8> The widthwise shrinkage percentages of the heat-shrinkable labels of Experimental Examples 1 to 8 were calculated as follows: (i) widthwise shrinkage percentage [%] when stored at 25°C; (ii) widthwise shrinkage percentage [%] after storage for 7 days in an atmosphere at a temperature of 55°C; (iii) the difference ((i) - (ii)) [%] between the widthwise shrinkage percentage when stored at 25°C and the widthwise shrinkage percentage after storage for 7 days in an atmosphere at a temperature of 55°C; (iv) maximum widthwise shrinkage percentage [%]; (v) natural shrinkage percentage [%]; (vi) widthwise shrinkage percentage [%] after storage for 1 day in an atmosphere at a temperature of 55°C and 30% humidity followed by storage for 6 days in an atmosphere at a temperature of 40°C and 90% humidity; and (vii) the difference ((i) - (vi)) [%] between the widthwise shrinkage percentage when stored at 25°C and the widthwise shrinkage percentage after storage for 1 day in an atmosphere at a temperature of 55°C and 30% humidity followed by storage for 6 days in an atmosphere at a temperature of 40°C and 90% humidity. The results are shown in Table 1.

[0051] (i) The widthwise shrinkage percentage [%] when stored at 25°C was calculated by immersing each of the heat-shrinkable labels of Experimental Examples 1 to 8 in a warm water bath at 60°C to 100°C for 10 seconds under no load immediately after production and immediately after storage in an atmosphere at a temperature of 25°C or less, using the following formula A' from the widthwise lengths of the heat-shrinkable labels 1 before and after immersion.

[0052] Width direction shrinkage rate [%]=100×[{(width direction length of heat shrinkable label before immersion)−(width direction length of heat shrinkable label after immersion)} / (width direction length of heat shrinkable label before immersion)] (Equation A′)

[0053] (ii) The widthwise shrinkage percentage [%] after storage for 7 days in an atmosphere at a temperature of 55°C was calculated by immersing the heat-shrinkable labels of Experimental Examples 1 to 8 in a warm water bath at 60°C to 100°C for 10 seconds under no load, immediately after storage (aging) in an atmosphere at a temperature of 55°C (humidity 1% to 2%) for 7 days in an atmosphere at a temperature of 25°C or less immediately after production of the heat-shrinkable labels, and then calculating the widthwise shrinkage percentage [%] after storage for 7 days in an atmosphere at a temperature of 55°C (humidity 1% to 2%) using the following formula C'.

[0054] Width direction shrinkage rate [%]=100×[{(width direction length of the heat-shrinkable label after aging before immersion)−(width direction length of the heat-shrinkable label after aging after immersion)} / (width direction length of the heat-shrinkable label after aging before immersion)] (Equation C′)

[0055] (iii) The shrinkage difference ((i) - (ii)) [%] between (i) the width direction shrinkage when stored at 25°C and (ii) the width direction shrinkage after 7 days of storage in an atmosphere at a temperature of 55°C was calculated by subtracting (ii) the width direction shrinkage [%] after 7 days of storage in an atmosphere at a temperature of 55°C from (i) the width direction shrinkage [%] when stored at 25°C.

[0056] (iv) The maximum shrinkage rate in the width direction [%] was calculated by immersing each of the heat-shrinkable labels of Experimental Examples 1 to 8 in a glycerin bath at 140°C for 10 seconds under no load immediately after production and immediately after storage in an atmosphere at a temperature of 25°C or less, and using the width direction length of the heat-shrinkable label 1 before and after immersion according to the following formula A''.

[0057] Maximum shrinkage rate in width direction [%]=100×[{(width direction length of heat-shrinkable label before immersion)−(width direction length of heat-shrinkable label after immersion)} / (width direction length of heat-shrinkable label before immersion)] (Equation A″)

[0058] (v) The natural shrinkage rate [%] was calculated from the widthwise length of the heat-shrinkable label 1 before and after storage (aging) for 7 days in an atmosphere at a temperature of 55°C or before and after storage (humidified aging) for 6 days in an atmosphere at a temperature of 40°C and humidity of 90% (without immersion in a hot water bath or a glycerin bath) using the following formula (B').

[0059] Natural shrinkage rate [%]=100×[{(width direction length of heat shrinkable label before aging or humidification aging)−(width direction length of heat shrinkable label after aging or humidification aging)} / (width direction length of heat shrinkable label before aging or humidification aging)] (Equation B′)

[0060] (vi) The widthwise shrinkage percentage [%] after storage in an atmosphere at a temperature of 55°C and a humidity of 30% for one day and then storage in an atmosphere at a temperature of 40°C and a humidity of 90% for six days (humidified aging) was calculated by immersing the heat-shrinkable labels of Experimental Examples 1 to 8, which had been stored in an atmosphere at a temperature of 25°C or less immediately after production of the heat-shrinkable labels, immediately after storage in an atmosphere at a temperature of 55°C and a humidity of 30% for one day, and immediately after storage in an atmosphere at a temperature of 40°C and a humidity of 90% for six days, in a warm water bath at 60°C to 100°C for 10 seconds without load, and calculating the widthwise shrinkage percentage [%] after storage in an atmosphere at a temperature of 55°C and a humidity of 30% for six days (humidified aging) in an atmosphere at a temperature of 40°C and a humidity of 90%.

[0061] Width direction shrinkage rate [%]=100×[{(width direction length of heat-shrinkable label after humidification aging before immersion)−(width direction length of heat-shrinkable label after humidification aging after immersion)} / (width direction length of heat-shrinkable label after humidification before immersion)] (Equation C″)

[0062] (vii) The difference in shrinkage ((i) - (vi) [%] between (i) the width direction shrinkage when stored at 25°C and (vi) the width direction shrinkage after storage for 1 day in an atmosphere at a temperature of 55°C and a humidity of 30% and then storage for 6 days in an atmosphere at a temperature of 40°C and a humidity of 90% (humidification aging) was calculated by subtracting (vi) the width direction shrinkage [%] after storage for 1 day in an atmosphere at a temperature of 55°C and a humidity of 30% and then storage for 6 days in an atmosphere at a temperature of 40°C and a humidity of 90% from (i) the width direction shrinkage [%] when stored at 25°C.

[0063] <Finish of Heat-Shrinkable Labels of Experimental Examples 1 to 8> The finish of the heat-shrinkable labels of Experimental Examples 1 to 8 was evaluated as follows: First, the flattened cylindrical heat-shrinkable labels (folded diameter (folded width) 114 mm) of Experimental Examples 1 to 8 after the above-mentioned storage at 25°C, after the above-mentioned aging, and after the above-mentioned humid aging were unfolded into a roughly cylindrical shape.

[0064] Next, a PET bottle having a body with a diameter of 65 mm (the diameter is the maximum diameter of the circular part, and is approximately hexagonal with six panels) and a shoulder located above the body and having a smaller diameter than the body was filled with tap water at 15° C. Next, the cylindrical heat-shrinkable labels of Experimental Examples 1 to 8 were fitted into the PET bottle, so that the heat-shrinkable labels of Experimental Examples 1 to 8 were respectively placed around the outer periphery of the PET bottle.

[0065] Next, the PET bottle containers fitted with the heat-shrinkable labels of Experimental Examples 1 to 8 were passed through a normal pressure steam tunnel (tunnel length 3 m, temperature inside the tunnel approximately 85°C (varies between 80°C and 90°C depending on the measurement position, the passage of the container, etc.)), and the heat-shrinkable label was heated for 3 seconds to cause heat shrinkage, thereby attaching it to the outer surface of the PET bottle container in close contact. Here, the steam outlet inside the steam tunnel was adjusted so that it was directed downwards on the PET bottle container in the front section of the steam tunnel, directed to an intermediate position in the middle section, and heated the entire container in the rear section. Furthermore, the required shrinkage rate at the maximum shrinkage position of the heat-shrinkable labels of Experimental Examples 1 to 8 at the uppermost end of the shoulder of the PET bottle container was set to 40 to 45%, taking into account variations in the heat-shrinkable label attachment position.

[0066] Next, the finish of the heat-shrinkable labels attached to the PET bottle containers of Experimental Examples 1 to 8 was visually evaluated according to the following criteria. The results are shown in Table 2.

[0067] (Criteria for evaluation of finish) A... Good finish with no wrinkles etc. B... Good finish with some wrinkles etc. C... Poor finish compared to A and B due to insufficient heat shrinkage D... Unsuitable for wear

[0068]

[0069]

[0070] <Evaluation> As is clear from the results in Tables 1 and 2, the heat-shrinkable labels of Experimental Examples 1 to 3, which satisfied at least all of the above requirements (1) to (4) for heat-shrinkable labels containing multilayer films, were able to reduce the natural shrinkage rate in the width direction after the aging or humid aging, compared to the heat-shrinkable label of Experimental Example 6, which did not satisfy at least the above requirements (1), (2), and (4). Furthermore, even after the aging or humid aging, the labels were able to improve the finish after attachment to a container by heating with steam.

[0071] Furthermore, as is clear from the results in Tables 1 and 2, the heat-shrinkable labels of Experimental Examples 4 and 5, which satisfy at least all of the above requirements (1) to (4) for heat-shrinkable labels containing polyester-based resin films, were able to reduce the natural shrinkage rate in the width direction after the aging or humid aging, compared to the heat-shrinkable labels of Experimental Examples 7 and 8, which do not satisfy at least the above requirement (4). Furthermore, even after the aging or humid aging, the labels were able to achieve a higher finish after attachment to a container by heating with steam.

[0072] Although the embodiments and experimental examples have been described above, it is also planned from the beginning that the configurations of the above-described embodiments and experimental examples may be appropriately combined.

[0073] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0074] The heat-shrinkable label of the embodiment can be used as a label that is attached to a container and displays information by being thermally shrunk by blowing steam onto the label and adhering to the container.

[0075] 1 heat-shrinkable label, 1a inner peripheral surface, 2 longitudinal direction, 2' imaginary axis, 3 width direction, 4 container, 10 heat-shrinkable film, 40 outer peripheral surface, 41 body portion, 42 shoulder portion, 43 mouth portion, 50 labeled container.

Claims

1. A heat-shrinkable label suitable for being attached to a container by being thermally shrunk by blowing steam onto it, the heat-shrinkable label comprising a multilayer film or a polyester resin film formed by laminating a first polyester resin layer, a polystyrene resin layer, and a second polyester resin layer in this order, and satisfying the following requirements (1) to (4): (1) A widthwise shrinkage rate of 1% or less after immersion in a 60°C hot water bath for 10 seconds; (2) A widthwise shrinkage rate of 10% or less after immersion in a 70°C hot water bath for 10 seconds; (3) A widthwise shrinkage rate of 40% or more after immersion in a 90°C hot water bath for 10 seconds; and (4) A widthwise shrinkage rate of 0.5% or less after storage for 7 days in an atmosphere at 55°C or after storage for 1 day in an atmosphere at 55°C and 30% humidity followed by storage for 6 days in an atmosphere at 40°C and 90% humidity.

2. The heat-shrinkable label according to claim 1, further satisfying the following requirement (5): (5) The shrinkage rate in the width direction after immersion in a warm water bath at 80°C for 10 seconds is more than 10% and not more than 50%.

3. The heat-shrinkable label according to claim 2, which satisfies at least the requirements (1) to (3) and (5) both before and after storage for 7 days in an atmosphere at a temperature of 55°C, or both before storage for 1 day in an atmosphere at a temperature of 55°C and 30% humidity followed by storage for 6 days in an atmosphere at a temperature of 40°C and 90% humidity and both after storage for 1 day in an atmosphere at a temperature of 55°C and 30% humidity followed by storage for 6 days in an atmosphere at a temperature of 40°C and 90% humidity.

4. A method for manufacturing a labeled container, comprising the steps of: placing a heat-shrinkable label according to any one of claims 1 to 3 so as to surround the outer periphery of a container; and blowing steam onto the heat-shrinkable label to heat-shrink the heat-shrinkable label and tightly attaching it to the outer periphery of the container.

5. A method for manufacturing a labeled container as described in claim 4, wherein the outer surface of the container comprises a body portion and a shoulder portion located above the body portion and having a smaller diameter than the body portion, and the required shrinkage rate at the maximum shrinkage position of the heat-shrinkable label at the shoulder portion is 40% or more.

6. A method for manufacturing a labeled container as described in claim 4, wherein the step of adhering the heat-shrinkable label to the outer peripheral surface of the container includes a step of blowing first steam onto a first portion of the heat-shrinkable label located below the container, and a step of blowing second steam onto a second portion of the heat-shrinkable label located above the container after the step of blowing the first steam.

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