JPH03187820A - Manufacture of thermal shrinkage label - Google Patents

Abstract

PURPOSE:To provide a thermal shrinkage label which prevents deformation of a heat resisting resin container during heat treatment, e.g. heating sterilization, such as boil, retort by a method wherein, in a cylindrical thermal shrinkage label formed such that the two ends of a film are overlapped with each other for joining, joining is effected such that all of an overlapped part between both ends of the film to be joined is within a joining region. CONSTITUTION:When two ends 8 and 9 of a film are overlapped with each other for joining so that the main shrinkage axis of a stretched flat thermal shrinkage film is extended in a peripheral direction, joining is effected so that a joining region C between positions 11 and 11' is contained in a joining region D between positions 12 and 12' where weld parts 10 range. A ratio between the overlapped part C and the joining range D can be changed according to the material, the shrinkage force, and the processing temperature of the film. The weld part 10 is a case in which welding is executed by an ultrasonic welding method, but a high frequency heating weld method, a normal Joule heat welding method, and an adhesive may be employed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a heat-shrinkable label that adheres tightly to the outer surface of a container such as a bottle or a can by heat-shrinking.

[Conventional technology] Heat-shrinkable labels have the following characteristics: they can be printed in multiple colors and are fashionable; they can neatly label curved surfaces of containers; they are water and weather resistant; they also serve as seals and help maintain quality. Because of this, it has been widely used in a variety of products to differentiate containers, improve safety, and improve hygiene.

These heat-shrinkable labels are often cylindrical shrinkable labels made by using a printed flat heat-shrinkable film and joining both ends of the film so that the main shrinkage axis is in the circumferential direction. FIG. 1 shows a sectional view of a joined portion of a cylindrical label joined by conventional typical ultrasonic welding, and FIG. 2 shows a plan view thereof.

When joining both ends of the heat-shrinkable film using this method, when both film ends 1.2 are overlapped and joined, the overlapping part A (corresponding to the crossed diagonal line part and the downward right diagonal line part) between g5.5'' Of these, the tip portion 4 of the film that will be on the container side when tightly attached to the container, and the upper film portion 7 that contacts the tip portion are connected to the joint area B (crossed) between the positions 6 and 6' where the welded portions 3 are continuous. (corresponding to the diagonal line area and the upper right diagonal line area), the label protrudes by about 1 to 10 mm.In the heat-shrinkable label manufactured by such a bonding method, after filling the labeled heat-resistant resin container with the contents, When heat treatment such as boiling, retorting, etc. is carried out, there is a drawback that deformation of the container tends to occur near the joint of the label.

[Problems to be Solved by the Invention] The present invention improves the drawbacks of conventional heat-shrinkable labels, and provides a method for producing heat-shrinkable labels that does not deform a heat-resistant resin container during heat treatment such as boiling, retorting, etc. It is on offer.

[Means for Solving the Problems] The present invention provides a cylindrical heat-shrinkable label in which both ends of a stretched flat heat-shrinkable film are overlapped and bonded so that the main shrinkage axis is in the circumferential direction. This method of manufacturing a heat-shrinkable label is characterized in that the films are joined so that all of the overlapping portions of both ends of the films to be joined are within the joining area.

The heat-shrinkable film used in the present invention is a thermoplastic resin film formed of a single layer or a composite layer of polypropylene, polycarbonate, polyester, polyvinyl chloride, polyethylene, polystyrene, or the like. Further, the heat-shrinkable film may be entirely or partially provided with an adhesive layer such as a hot-melt adhesive on the side in contact with the outer surface of the container, and printing may be performed on either the front or back of the film.

Next, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 3 is a sectional view of a joint portion of a cylindrical heat-shrinkable label according to an embodiment of the manufacturing method of the present invention, and FIG. 4 is a plan view thereof.

As shown in FIGS. 3 and 4, the method for producing a cylindrical heat-shrinkable label of the present invention is to
When overlapping and joining, the joining area C between positions 11 and 11' (corresponding to the crossed diagonal lines) is the joining area D between positions 12 and 12'' where the welded parts 10 are continuous (corresponding to the crossed diagonal lines). The bonding is performed so that the bonding area is included in the overlapping area C and the diagonally shaded area on the upper right.The ratio between the overlapping area C and the bonding area can be changed depending on the material of the film, shrinkage force, processing temperature, etc. The welded portion 10 shown in Fig. 4 is an example of welding by ultrasonic welding, but it may also be welded by high frequency heat welding, normal Joule heat welding, or adhesive, and the welding pattern may also be the same as the fourth welding pattern. It does not matter in particular whether it is a line of bars as shown in the figure, a mesh shape, a dot shape, or a solid solid label.The cylindrical heat shrinkable label produced by the method of the present invention is
~4 As shown in Figure 4, all of the overlapped portions C of the films are within the bonding area, and the leading end portion of the film does not protrude outside the bonding area. By doing so, it is possible to obtain a heat-shrinkable label that does not deform the container during heat treatment.

Deformation of the container due to heat shrinkage of the label is thought to occur for the following reasons.

The leading edge portion 4 of the film outside the bonding area as shown in Figures 1 and 2
When a heat-shrinkable label is attached to a container, heat-shrinked in a hot air oven, etc., and adhered to the outer surface of the container, the container is filled with the contents and subjected to heat sterilization such as boiling or retorting. The label attempts to shrink further during heat treatment such as in a retort, but this is hindered by the container, creating tension and applying a tightening force that tightens the container from the outside. It's going to happen. At this time, both films at the joint portion tend to deform due to the unbalance caused by the presence of the film tip portion 4 and the tension so that the film tip portion 4 pushes the container from the outside.

Therefore, the outer surface of the container in the vicinity of the joining part of the label, that is, the portion of the outer surface of the container that is in close contact with the leading end portion 4 of the film, is subjected to a larger external force toward the inside of the container than other parts of the container.

In addition, since one end of the film tip portion 4 is not fixed, it can be thermally shrunk relatively freely, so the apparent thickness may increase due to an increase in thickness due to shrinkage or uneven shrinkage due to the welding state, and the tip portion 4 may Since the outer surface of the container is pressed by the upper film 7 that is in contact with this, the outer surface of the container is further subjected to external force toward the inside of the container as the thickness increases. Therefore, due to the action of such an inward external force and the circumferential tightening force caused by the shrinkage of the label, stress is concentrated on the container at the portion in close contact with the film tip portion 4 near the label joint. During heat treatment for heat sterilization, such as boiling and retorting, the contents of the container must be kept at a predetermined temperature for a predetermined period of time, so the heat-resistant resin container is also heated to a predetermined temperature, reducing the rigidity of the container. do. For this reason, when a heat-shrinkable label with a film tip 4 is used, the container is subject to stress concentration and tends to be deformed near the joint.

According to the present invention, the entire portion where the films are overlapped is within the bonding area, and the leading end portion of the film does not protrude outside the bonding area. Therefore, stress concentration as described above does not occur, and it is thought that the heat-resistant resin container will not be deformed even if it is subjected to heat treatment such as boiling, retorting, or other heat sterilization.

Embodiments of the present invention are shown in accordance with FIGS. 3 and 4.

A transparent axially stretched polypropylene film with a thickness of 50μ and a shrinkage rate of 50% at 100°C was printed on the inside and further coated with 5μ of an ethylene-vinyl acetate copolymer hot melt adhesive, so that the shrinkage axis was in the circumferential direction. A cylindrical label 14 having a circumference of 205 mm was produced by overlapping both ends of the film 8.9 and welding using an ultrasonic welding machine so that the overlapping portion C was entirely within the joining area. Next, as shown in FIG. 5, a heat-resistant m fat container 13 with a bottom diameter of 65 mm, a bottom diameter of 55 mm, and a height of 32 mm is made by vacuum forming a multilayer sheet of polypropylene/saponified ethylene vinyl acetate copolymer/polypropylene. The cylindrical label 14 is attached to the container and left in an atmosphere of 120° C. for 20 seconds to make it adhere to the container, and then the container is filled with contents such as a water bottle, and is made of a multilayer film of nylon/polypropylene or the like. 80μ
It was sealed with a lid material having a thickness of 15 mm. The content is 120 extra large containers.
Even after retort sterilization at ℃ for 20 minutes, there was no deformation of the container at all. Furthermore, in the case of a conventional method using a shrink label in which the overlapping portion of the films protruded from the bonding area, which was carried out at the same time, a large groove-like deformation occurred in the container near the bonding area, and a product with commercial value could not be obtained.

[Effects of the invention] By using the heat shrinkable label according to the present invention, voile,
It is possible to obtain a heat-resistant resin container with commercial value that does not undergo deformation during heat treatment such as heat sterilization of a retort or the like.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a joint part of a cylindrical heat-shrinkable label manufactured by a conventional method, FIG. 2 is a plan view of the same, and FIG. 3 is a joint part of a cylindrical heat-shrinkable label according to an embodiment of the method of the present invention. 4 is a plan view of the same, and FIG. 5 is a sectional view of a container in which a heat-shrinkable label is tightly attached by heat-shrinking, the container is filled with contents and then sealed with a lid material. l... Upper film edge, 2... Container side film edge, 3...
・Welded part, 4...Film tip, 5.5' ・
The position of both ends of the overlapping part of both ends of the film, 6.6'・
・Positions of both ends of the joining area, 7. Upper film portion in contact with the tip, 8. Upper film edge, 9. Container side film edge, 10. Welded portion, 11.11” ・Both ends of the overlapping portion of both film ends Positions, 12, 12' - Both end positions of the bonding area, 13... Heat-resistant resin container, 14 - Heat shrinkable label attached to the container, 15... Lid. A, B... Overlapping parts of both ends of the film, C ,D...
TP document of joint area drawing (L with changes to content) Figure 1 Figure 2 Circumferential direction Circumferential direction Procedure amendment C method) % formula % ■, Indication of incident 1999 Patent Application No. 319031 2, Invention Name of heat shrink label manufacturing method 3, relationship with the case of the person making the amendment

Claims (1)

[Claims] (1) In a cylindrical heat-shrinkable label in which both ends of a stretched flat heat-shrinkable film are joined so that the main shrinkage axis is in the circumferential direction, the overlapping portion of both ends of the film to be joined is A method of manufacturing a cylindrical heat-shrinkable label that is bonded so that everything is within the bonding area.