JPH06102474B2 - How to seal a retort container - Google Patents

Description

The present invention relates to a method for sealing a retort container filled with contents.

[Conventional technology]

Conventional sealing methods using the heat sealing method include a one-step sealing method and a two-step sealing method. As the one-stage sealing method,
For example, a method of covering the container opening with a plastic film and sealing the container flange of the opening by applying a line seal in a ring shape, a method of sealing the entire surface of the container flange, and a spot adhesion to the entire surface of the container flange There is a knurled seal to do.

Also, as the technology related to the two-stage sealing method,
A primary seal is made by closely heating to the upper surface of the brim at the top of the container described in No. 31061 (packaging and sealing form in containers such as egg tofu), and then forming a V-shaped groove with the brim from above the secondary seal. The two-stage sealing technique for carrying out the method described in JP-A-62-193907 (easily openable container sealing method and device) is applied to temporarily heat and pressurize the entire surface of the flange portion, and then to heat and press in a ring shape. A two-stage sealing technique for performing ring sealing by means of a ring shape, as described in Japanese Patent Laid-Open No. 52-128790 (Tray packaging method), in which the leak paths toward the outside of the peripheral edge of the tray are separated from the first welding portion and are independent of each other. A two-stage sealing technique in which a first welded seal is formed so as to form a non-welded portion, and then a second welded seal is formed outside the peripheral portion so that a non-welded portion is formed, and Japanese Patent Publication No.
-43353 (sealing method for heat-sealed aluminum container),
There is a two-stage sealing technique in which a primary seal having a gap for removing residual air in the package is performed, and then a secondary seal is performed for complete heat sealing.

Needless to say, the seal is applied after filling the contents, but the contents are often scattered during the filling, and the contents often adhere to the container sealing part, for example, the container flange part. In addition, when full filling is performed, a considerable amount of contents often remain on the flange portion of the container. When the lid material is sealed on the container flange portion by the above sealing method in such a state, the following problems occur.

(I) According to the method in which the container flange portion is line-sealed in a ring shape, there are problems that the contents remain on the inner and outer portions of the seal and the lid material on the outer portion of the seal is curled to impair the appearance.

(Ii) According to the method of sealing the entire surface of the container flange,
In order to obtain sufficient sealing strength (for example, retort resistance), it is necessary to seal under relatively strong conditions, so the contents remaining in the flange part foam, which impairs the aesthetics of the flange part and causes a sealing failure due to the foaming. There is a problem that occurs.

(Iii) According to the method of knurling sealing, which adheres spotwise to the entire surface of the flange of the container, in order to obtain sufficient sealing strength (for example, retort resistance), it is necessary to seal under fairly strong conditions. The remaining contents foam and cause poor sealing. As a result, there is a problem that the inside and outside of the container communicate with each other and the contents are rotted.

(Iv) According to the method described in Japanese Utility Model Publication No. 62-31061 and Japanese Patent Application Laid-Open No. 62-193907, in which the entire surface is sealed and then the ring is sealed, there is a problem that the residual contents foam and the appearance is impaired. .

[Problems to be Solved by the Invention]

It is an object of the present invention to provide a method for sealing a retort container, which has a sufficient seal strength and is excellent in the appearance of the container seal portion.

[Means for Solving the Problems]

The present invention was made on the basis of the finding that if the opening of the retort container is first line-sealed and then the knurled seal is applied with a weak force, no foaming of the food adhering to the sealing surface can be seen. is there.

That is, in the present invention, the opening of the retort container filled with the contents is subjected to a line seal having a width of 0.5 to 2.5 mm by heat sealing to seal the container, and then a knurled seal is applied to a portion including the seal. A method for sealing a retort container, the method comprising:

According to an aspect of the present invention, a plastic film 4 is superposed on a container 1 having an opening 2 in the opening itself, preferably as shown in FIG. 1 and having a flange 3 around the opening. To cover the opening with a line seal 5 on the flange.
And the opening 22 of the bag-like container 21 such as the retort pouch shown in FIG.
A second mode and the like in which the line seal 25 and the knurled seal 26 are provided in the opening 22 are included.

It is preferable that the container used in the first aspect has a flange or flange (width 5 to 12 mm) at the upper end of the container.
Polypropylene, polyethylene, polyvinylidene chloride,
Examples thereof include those formed of a thermoplastic resin such as an ethylene vinyl alcohol copolymer, or those formed of the above resin or a laminate of the above resin and steel.

As the lid material for covering the opening of the container, any material that can be welded to the container may be used, and examples thereof include resin films such as polypropylene, polyethylene terephthalate, polyvinylidene chloride, and nylon, aluminum foil, and laminates thereof. The thickness of these lids is 70-140μ, preferably 85
〜105μ is suitable.

The retort pouch used in the second embodiment is formed of a thermoplastic resin such as polypropylene, polyethylene, polyvinylidene chloride, or ethylene vinyl alcohol copolymer, a laminate of the resin, or a laminate of the resin and an aluminum foil. An example is a bag-shaped container. The thickness of the container wall is preferably 70 to 230 μm.

In the present invention, after filling the above-mentioned container with the contents, in the first embodiment, the opening is covered with a film-like lid material,
In this mode, the opening is closed and sealed.

The contents to be filled here may be any as long as they can withstand retort sterilization, and may be liquid substances or paste substances and those containing solid substances. Specific examples include soy milk, egg tofu, yogurt and the like.

The method of filling the contents in the container can be carried out by an ordinary method, and particularly in the case of the present invention, when a filling method in which a relatively large amount of contents remains on the container flange, such as full-filling, is adopted. Shows excellent effects. At this time, it is possible to effectively seal without removing the contents attached to the flange portion.

In the present invention, first, the seal width is 0.5 to 2.5 mm, preferably 1 to
A 2 mm line seal is applied by heat sealing so that the container is sealed. If the seal width is smaller than 0.5 mm,
There is a risk of poor sealing, and conversely, if the thickness is greater than 2.5 mm, there is a risk of the contents remaining in the sealed portion, causing foaming. The wire seal should be 170-220 ℃ so that the seal strength after the seal will be 2.6-6.8kg / 15mm.
It is recommended that the sealing surface pressure be 10 to 40 kg / cm ² for 1.0 to 3.0 seconds. This gives a seal strength of 2.3k after retort sterilization.
It can be g / 15mm (container / packaging standard based on the Minister of Health and Welfare standard for container-packed pressurized heat sterilized foods: 2.3kg / 15mm or more) to 6.0kg / 15mm. When performing the above treatment, if the seal strength is lower than 2.6 kg / 15 mm, the seal strength of 2.3 kg / 15 mm or more cannot be obtained after the retort sterilization treatment. On the other hand, when the seal strength is higher than 6.8 kg / 15 mm, there is a possibility that the seal may be melted or cut during sealing. Further, when a transparent film is used as the packaging material, there arises a problem that the sealed portion becomes cloudy. Furthermore, a considerable force is required to open the sealed portion. Seal surface pressure
If it is weaker than 10 kg / cm ² , it will not be fully sealed,
Poor sealing may occur, and some parts may not be fully sealed and some may not. Further, if it is stronger than 40 kg / cm ² , the seal strength becomes too strong, so that the easy-open property is deteriorated,
This is because the problem that the lid material is cut occurs.

More preferable conditions are 180 ℃ ~ 210 ℃, seal surface pressure 15 ~
It is 30 kg / cm ² .

The seal surface pressure is a value obtained by dividing the load of the hot platen by the area of the seal portion, and means the pressure applied to the seal portion.

In the present invention, next, a knurled seal is applied to a portion including the line seal. Here, the knurled seal is a seal in which the seal traces are in a grid pattern, and the ratio of the knurled part to the non-sealed part is 1/9 to 6
I say something that is / 4. The knurled seal only needs to be sealed under such conditions that the sealed portion does not peel off,
For example, 170 to 240 ℃, 1 to 3 seconds, seal surface pressure 10 to 40 kg / cm ²
It is good to do it in.

The width and the like of the knurled seal are not particularly limited, but the entire surface of the container flange portion or the container flange portion outside the line seal is preferable, and in the second aspect, the entire length from the line seal to the opening portion is preferable. The seal width is 3 to 20 mm, preferably 5 to 12 mm.

The container sealed by the above method is sterilized by retort according to a conventional method.

[Operation of the invention]

Since the seal width of the ring-shaped line seal according to the present invention is narrow, the contents do not remain in the line seal portion. Therefore, even if the wire seal is applied under relatively strong conditions, foaming does not occur. That is, since a sealing failure due to foaming or the like does not occur, it is possible to provide a reliable seal with sufficient sealing strength.

The knurled seal to be applied next does not require a sealing treatment under considerably strong conditions because the container flange portion and the lid member have already been sufficiently bonded by the line seal. That is,
The sealing treatment may be performed under the condition that the knurled seal portion does not peel off. Therefore, the knurl seal treatment does not cause foaming of the contents remaining in the container flange portion other than the line seal portion, so that the aesthetic appearance of the container flange portion is not impaired, and the knurl seal is a spot-like seal. As a result, the appearance is aesthetically pleasing. Therefore, even if the contents remain on the container flange, the knurled seal does not impair the aesthetics of the container flange and prevents foaming.

〔The invention's effect〕

According to the sealing method of the present invention, it is possible to obtain sufficient sealing strength even if the contents remain on the container flange portion and the like, and further, the aesthetic appearance of the container flange portion is not impaired. Further, since the sealing method according to the present invention does not cause foaming at all in the container sealing portion, there is no need to perform sealing under considerably strong conditions because of concern about foaming, and thus easy peeling is also obtained.

Next, the present invention will be described with reference to examples.

〔Example〕

Example 1 A container with a flange of the form shown in FIG. 1 (width of the flange portion
7mm, capacity 150ml, container wall thickness 700μ, polypropylene) was filled with 150ml soymilk coagulant mixture, and the upper opening was made of PET / nylon / PP 95μ thick film (1
1 cm x 11 cm) and a 1.5 mm wide line seal on the flange.
The film was fused at 190 ° C. for 1.6 seconds under the condition of 24 kg / cm ² and the film was fused to the container flange to seal the container.

Next, a knurled seal was applied on the line seal with a width of 7 mm under the conditions of 200 ° C., 1.6 seconds, and 30 kg / cm ² .

After that, retort sterilization treatment was performed at 121 ° C. for 22 minutes. The seal strength (heat sealing strength) after retort sterilization was 3.1 kg / 15 mm. The heat sealing strength was measured by the following method (the same applies hereinafter).

Heat-sealing strength measurement method Cut the heat-sealed portion of the sealed packaging container by 15 mm and open it, pull both ends of the opened portion vertically at a speed of 300 mm / min, and load the heat-sealed portion up to the maximum load. Was measured (device name: Shopper type tensile tester, manufactured by Nippon Rigaku Kogyo Co., Ltd.).

Comparative Example 1 The container was sealed in the same manner as in Example 1 except that the knurling seal was not performed.

Comparative Example 2 Instead of the wire seal and the knurled seal in Example 1, the entire surface of the container flange was sealed under the conditions of 200 ° C., 1.6 seconds and 10 kg / cm ² .

Comparative Example 3 Instead of the wire seal and the knurled seal in Example 1, the entire surface of the container flange was knurled under the conditions of 230 ° C., 1.6 seconds and 30 kg / cm ² .

Comparative Example 4 A container was prepared in the same manner as in Example 1 except that knurl sealing was first performed at 205 ° C. for 1.6 seconds and 30 kg / cm ² , and then line sealing was performed at 185 ° C. for 1.6 seconds and 24 kg / cm ² . Sealed.

Example 2 A standing pouch made of PET / aluminum / PP (120 mm × 170 mm, capacity: 200 ml) having a thickness of 95 μ was filled with 200 ml of soymilk, and as shown in FIG.
A width line seal was applied at 190 ° C. for 1.6 seconds at 24 kg / cm ² .

Next, apply a 6 mm wide knurled seal at 200 ° C for 1.6 seconds at 30 kg / cm.
^It was applied under the condition of ² .

Then, retort sterilization was performed under the conditions of 121 ° C. and 18 minutes.

Table 1 collectively shows the heat-sealing strength and the appearance of the sealed portion at the time of sealing and after the retort sterilization treatment when sealing was performed by the methods of Examples 1 and 2 and Comparative Example.

From the results in Table-1, the line seal alone (Comparative Example 1) has an extremely poor aesthetic appearance on the outer side of the seal portion, and the whole surface seal (Comparative Example 2) and the knurled seal alone (Comparative Example 3) are suitable for foods attached to the seal surface. There is a problem that foaming is generated. It is also found that the foaming is not improved even by the method of first performing the knurling seal and then performing the line sealing (Comparative Example 4).

On the other hand, according to the present invention (Examples 1 and 2), it is possible to obtain an excellent sealed container in which the sealing surface is free from foaming.

[Brief description of drawings]

FIG. 1 is a semi-longitudinal cross-sectional perspective view of a container sealed by the method of the present invention, FIG. 2 is an enlarged plan view of a sealed container flange portion, and FIG. 3 is a part of a knurled seal platen. FIG. 4 is an enlarged plan view from below, and FIG. 4 is a perspective view showing a part of the retort pouch container sealed by the method of the present invention. In the figure 1,21 …… Container 2,12,22 …… Opening part 3,13 …… Flange part 4 …… Film 5,15,25 …… Line seal 6,16,26 …… Knurl seal 18 …… heat Board 20 ... It is a convex part.

Claims (1)

[Claims] 1. A retort container filled with contents is heat-sealed to form a line seal having a width of 0.5 to 2.5 mm to seal the container, and then a knurled seal is applied to a portion including the seal. A characteristic method for sealing a retort container.