JPH0811577B2 - Packaging method for heat shrinkable packaging - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to soft drinks, lactic acid bacterium drinks, food and drink containers such as marine products, containers for pharmaceuticals, miscellaneous goods, articles such as industrial materials, labels made of heat-shrinkable films, cap seals, The present invention relates to a packaging method of covering with a packaging material such as a safety shield for preventing foreign matter mixture and then heating and shrinking.

[0002]

2. Description of the Related Art In recent years, heat-shrinkable films of thermoplastics such as vinyl chloride have been widely used as packaging materials for labels, cap seals, foreign substance contamination prevention safety shields, etc. when packaging the above-mentioned articles. Is coming. In particular, there has been conventionally known a method in which an article coated with a heat-shrinkable film is introduced into a heating tunnel furnace commonly referred to as a shrink tunnel furnace, and a film as a packaging material is heat-shrinked to be packaged. This method is widely used because it can efficiently pack a large number of articles continuously.

The heating and shrinking means in the shrink tunnel furnace are as follows: 1) hot air blowing heating method (for example, Japanese Patent Publication No. 48)
-44096, see Japanese Utility Model Publication No. 49-28124) and 2) steam heating method (see Japanese Utility Model Publication No. 60-99210),
Each is widely used. The former hot air blowing method is a method in which an article covered with a heat-shrinkable film is introduced into a tunnel, and hot air heated with a heater is blown onto the article to shrink the film, but the heat capacity of the hot air is small, so it is high speed. When a large amount of articles are heat-shrink-wrapped, local wrinkle-like wrinkles are often generated due to uneven shrinkage, which impairs the aesthetics of products that emphasize appearance. Therefore,
In order to improve this, it is necessary to take measures such as (a) lengthening the tunnel furnace, (b) increasing the volume of hot air, and (c) increasing the temperature of hot air, but the method (a) requires high equipment costs. A wide space is required, and the method of (b) may hinder productivity because the articles may be blown off or fallen down by hot air in the tunnel, and the method of (c) involves heating the articles locally, There are drawbacks such as deformation, burning, and further thermal decomposition, and the need to take measures against heat to the device itself.

Since the latter steam heating method uses a steam as a heating medium, it has a large heat capacity as compared with the former, and a large amount of articles can be shrink-wrapped at high speed. However, since steam has a large latent heat of condensation, the heat-shrinkable packaging material undergoes rapid shrinkage, resulting in uneven coating finish, and flapping-like localized shrinkage wrinkles due to condensed water adhering to the label. Printed figures and letters become distorted, and the entire film is distorted, resulting in poor appearance. Moreover, since the surface of the coated article gets wet with condensed water, it is necessary to provide a drying step as a post step. Therefore, 3) a heating method using radiant heat (see, for example, Japanese Utility Model Publication Nos. 50-33398 and -29008), and 4) a heating method using hot water (Actual Publication No. 51-35484, Japanese Patent Publication No. 58-55059). Although Japanese Utility Model Laid-Open No. 60-32207) was also proposed, the method of 3) is simple in equipment, but uneven shrinkage or burning is likely to occur depending on the distance between the heat source and the package, and the method of 4) is packaged. However, there is a limitation in use because it is in contact with hot water, and there is a drawback that equipment for drying a package wet with hot water must be provided.

[0005]

Therefore, it is an object of the present invention to use steam as a heating medium,
It is an object of the present invention to provide a packaging method for a high-quality and highly productive heat-shrinkable packaging material which is less likely to cause uneven coating finish or pock-like shrinking wrinkles and does not require a large-scale drying step.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the use of heated steam results in a shortage of heat capacity and steam heating which are disadvantages of the conventional hot air blowing method. The disadvantage of the method is that it prevents the unevenness of the finish of coating and the occurrence of flutter-like shrinkage unevenness due to the condensed water adhering at the start of shrinkage, and reduces the amount of condensed water to simplify or omit the drying process as a post process. Heading, completed the present invention. That is, the packaging method of the heat-shrinkable packaging material according to the present invention covers the article with the heat-shrinkable packaging material, preferably introduces it into the tunnel furnace, and the surface temperature of the heat-shrinkable packaging material is 40 by hot air.
Above the glass transition temperature, especially between 50 and 70 ℃
Until preheated and then with steam heated to 105 ° C. or higher after the pressure was reduced to once atmospheric pressure, it is characterized in that to heat shrinking the heat-shrinkable packaging material.

FIG. 1 showing an embodiment of the present invention.
It will be described in detail based on. A conveying device 2 composed of a roller conveyor or the like penetrates through the tunnel furnace 1 having a furnace length of 2 m, and the article 3 covered with the heat-shrinkable film is introduced into the tunnel furnace 1 by the conveying device 2. 4 is fed into the furnace, passes through it, and is discharged out of the machine through an outlet 5. The inside of the tunnel furnace 1 is composed of a preheating section A and a heat shrinking section B. In the preheating section A, the air from the supply source 6 is guided to the heater 8 by the pump 7, where it is preheated and the furnace hole 9 blows it. It is blown out inside. In this hot air
Thus, articles coated with the heat-shrinkable packaging material heat-shrinkable packaging
The surface temperature of the packaging material is preheated to near the glass transition point, and the remaining air is discharged from the exhaust port 10 to the outside of the machine. In the preheating section A, the detector 11 detects the temperature, and by controlling the heater 8, the temperature is adjusted to be constant.

When the preheating temperature of air in the preheating section A is lower than the glass transition temperature of the heat shrinkable packaging material coated with the article by 20 ° C. or more, not only the condensed water of the steam blown in the heat shrinking section B increases but also the water droplets. Since it also becomes larger, contraction tends to become distorted. Therefore, it is necessary to preheat the surface of the heat-shrinkable packaging material up to near the glass transition point where the shrinkage of the heat-shrinkable packaging material starts. If the preheating temperature of the air is too high, the part where the hot air is blown strongly contracts greatly, and the part other than that relaxes, so the contraction completes distorted.
Many appearance defects occur. Therefore hot air temperature
Optimally, the temperature is preheated to be within ± 20 ° C of the glass transition temperature of the heat-shrinkable packaging material. Heat shrink
The article in which the surface temperature of the flexible packaging material is preheated to the vicinity of the glass transition point is transferred to the heat shrinking section B by the carrying device 2,
Heat shrinks by being sprayed with steam heated to 5 ° C or higher
The flexible packaging material is heat-shrinked.

In the steam used in the conventional steam type shrink tunnel furnace, the steam generated in the boiler is adjusted to a desired pressure by a pressure reducing valve and then sprayed. The steam pressure was increased to raise the temperature to a high level, but the latent heat of condensation is large and the amount of condensed water is large, so that the packaging material contracts rapidly and tends to become distorted. Also, since a large amount of water is condensed on the surface, a large drying device is required in the post process. In the present invention, the steam generated in the boiler 15 is reduced by a pressure reducing valve.
After depressurizing to almost normal pressure with 16, the heater 17 heats up to a desired temperature of 105 ℃ or more and blows out from the outlet 18, so the latent heat is smaller than the conventional steam, and the condensed water is not small. The shrinkage of the packaging material is relaxed as compared with the conventional method. Further, since the condensed water content is small, the surface of the article is less wetted, and there is an advantage that the dryer in the subsequent process is small or can be omitted depending on the case.

Generally, steam used for heating is 105 ° C.
The lower the heat capacity is, the smaller the heat capacity is, and the amount of heat for heat shrinkage is supplied by the condensation of water, so that the condensation starts almost at the same time as the spraying. On the other hand, when steam heated to 105 ° C or more is used, water does not condense until the temperature of the sprayed steam drops to 100 ° C, so that the shrinkage is gentle and the condensed water decreases as described above. It is desirable that the upper limit for heating steam is 200 ℃ or less, and if it exceeds 200 ℃, the sprayed steam may cause deformation or deterioration of the product, so select the heating temperature according to the product to be packaged. There is a need to. This control is performed by detecting with the detector 19 and controlling the heater 17. The temperature setting in the heat shrinking section B is performed while observing the covering state of the article 3.
Further, the steam having the lowered temperature after heating is discharged from the system through the exhaust port 20.

The heat-shrinkable packaging material used in the present invention is, for example, polyvinyl chloride, polystyrene, polypropylene,
Examples thereof include a heat-shrinkable film obtained by stretching a thermoplastic resin such as polyethylene and polyethylene terephthalate, or a laminated film in which two or more kinds of these are combined.

[0012]

EXAMPLES Specific embodiments of the present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited to the description of these Examples. Examples 1-6. A polyethylene terephthalate bottle 21 having the shape shown in FIG. 2 is filled with water at 25 ° C., and a shrink label made of polyvinyl chloride (glass transition temperature: 79 ° C.) having the shape shown in the drawing is used.
The sample was covered with 22 and the heat shrink wrapping test was performed 10 times for each example under the conditions shown in Table 1 using the apparatus (furnace type a) shown in FIG.

Comparative Example 1. FIG. 3 shows a conventional hot-blast stove (kind of furnace b), and this tunnel furnace 31 is provided with a transfer device 32 similar to that shown in FIG. Air is introduced from a supply source 36 to a heater 38 by a pump 37, where it is heated to a predetermined temperature and supplied into the furnace through a fumarole 39. In addition, 33 is an exhaust port, 34 is a detector, and the total length of the furnace is 2 m as in FIG. Using this apparatus, a heat shrink wrapping test was conducted under the conditions shown in Table 1 in the same manner as in the examples.

Comparative Example 2. FIG. 4 shows a conventional steam tunnel furnace (furnace type c), which also has a conveying device 42 that penetrates through the tunnel furnace 41. The steam is a boiler.
It is supplied into the furnace from 45 through a pressure reducing valve 46 and from an outlet 48. 43 is an exhaust port, 44 is a detector, and the total length of the furnace is shown in FIG.
It is 2m like that of the above. The major difference between this furnace and the device of the present invention is the lack of a preheat section and the lack of heater in the steam. Using this apparatus, a heat shrink wrapping test was conducted under the conditions shown in Table 1 in the same manner as in the examples.

In the heat shrink wrapping of each example, the shrink wrapping condition of the label in the annular groove 23 at the center of the bottle, the occurrence of speckled distortion when the label shrinks at the shoulder 24, and the wet condition of the label surface are observed. Then, these shrinkage conditions were evaluated according to the following criteria, and the number of occurrences of defects per 10 times is also shown in Table 1.・ Shrinkage packaging of labels: Ratio of incomplete shrinkage or incomplete wrinkling.・ Spotted strain occurrence rate: The ratio of spotted strains. -Wet state of label surface: Observation of the wet state of the surface of the package coming out of the tunnel furnace.

[0016]

[Table 1]

[0017]

According to the method for packaging a heat-shrinkable packaging material of the present invention, even though steam is used as the heating medium, spot-like distortion and shrinkage wrinkles are less likely to occur as compared with the conventional method. In addition, a large-scale drying step is not required, and a high-quality package can be easily obtained with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of an apparatus (furnace type a) for carrying out the method of the present invention.

FIG. 2 is a front view of packages used in Examples and Comparative Examples.

3 is a schematic explanatory view of an apparatus (furnace type b) according to the conventional method used in Comparative Example 1. FIG.

FIG. 4 is a schematic explanatory view of an apparatus (furnace type c) according to the conventional method used in Comparative Example 2.

[Explanation of main symbols]

1, 31, 41 …… Tunnel furnace, 3, 21 …… Goods, 22 …… Heat-shrinkable packaging material.

Claims (1)

[Claims] 1. An article is coated with a heat-shrinkable packaging material to obtain a heat-shrinkable article .
Packaging material surface temperature hot air by 40 ° C. or more of, preheated to near the glass transition temperature, and then once the pressure was reduced to atmospheric pressure
Heat-shrinkable packaging material using steam heated to 105 ° C or higher
A method for packaging a heat-shrinkable packaging material, which comprises heat-shrinking.