JPH0798530B2 - Partial lid double seal method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for heat-sealing a lid at the edge of a container. More specifically, the present invention relates to a method of partially double heat sealing a lid to the rim of a container.

[Prior Art] As consumer life becomes richer, foods using molded containers have come to be widely available in the secondary market. In particular, in recent years, applications have been diversified such as soft drinks such as juice, chilled desserts such as pudding, yogurt and coffee jelly, and cup ramen.

Basically, the packaging in these molded containers requires (1) protection of contents, (2) ease and safety of transportation / storage / load handling, and (3) suitability for packaging machines. However, these requirements are a matter of producer side,
There are other demanding issues for consumers.

From the consumer's point of view, it is strongly desired that the container lid can be eaten immediately after purchase if it is purchased, and for that reason, it is easy to open the lid even for children with weak muscles and the elderly. It is necessary to have openness. Furthermore, it may be necessary that there is no problem in food hygiene and that the contents can be visually observed from the outside depending on the product.

Under such circumstances, it is required to develop a sealing method that satisfies the above requirements including the easy-open property as much as possible.

[Problems to be Solved by the Invention] As an easy-open packaging method, a lid material in which a hot-melt adhesive is applied to an aluminum foil has been often used. The adhesive application surface of this lid material is applied to the rim of the container, and heat and pressure are applied from above.

In such a sealing method, there is a large variation in peel strength due to fluctuations in the sealing temperature, and the easy open seal is unstable. In fact, when the lid is opened, the adhesive strength is often too high and the lid itself is torn, which does not satisfy the requirement for easy openness.

Further, there is a drawback that the adhesive on the sealing surface remains when the lid material is peeled off.

Recently, research on adhesives has progressed, and an extrudable compound containing ethylene vinyl acetate (hereinafter referred to as EVA), polystyrene (hereinafter referred to as PS), polypropylene (hereinafter referred to as PP) resin as a main component, which is suitable for easy opening. Has been developed, and lid materials such as aluminum foil coated with this adhesive, polyethylene terephthalate (hereinafter referred to as PET), and paper are used.

However, even if such a new kind of adhesive is used,
Not all the above-mentioned problems when the lid is peeled off have been solved. For example, if the entire circumference of the rim is heat-sealed under the same conditions, the overall peel strength is either strong or weak. If it is strong, the same problem as the conventional adhesive occurs, and if it is weak, the problem of poor sealing occurs. In other words, the easy-open property and the high sealing property are properties that cannot be originally compatible with each other.

[Object of the Invention] Therefore, an object of the present invention is to provide a lid sealing method that can achieve both easy-open property and high sealing property.

[Means for Solving the Problems] As a means for solving the above problems and achieving the object of the present invention, the present invention, when heat sealing a lid to the upper end surface of the rim of the molding container, A lid is placed on the upper end surface, and the entire circumference of the outer peripheral edge of the lid from the upper surface of the lid along the upper end surface is heat-sealed at a relatively low temperature, and then a part of the outer peripheral edge of the lid is firstly sealed. There is provided a partial lid double sealing method, characterized in that the heat sealing is performed again at a temperature higher than the temperature at the time of heat sealing.

[Operation] As described above, the method of the present invention comprises heat-sealing the entire circumference of the rim at a low temperature, and then resealing a part of the rim at a high temperature.

When treated in this manner, the peel strength of the portion reheat-sealed at a high temperature is significantly higher than the peel strength of the low-temperature heat-sealed portion.

As a practical matter, in some cases, only a portion of the lid needs to be detached from the edge of the container. For example, in the case of a soft drink container, a space for inserting a straw may be provided. Thus, it can be solved by a dangerous use such as sharply cutting the tip of the straw, piercing it with the lid and inserting it into the container. Further, in the case of a cup ramen container, only the portion necessary for pouring hot water can be peeled off. This is because the lid is replaced after pouring boiling water.

Furthermore, if the lid is completely separated from the container, it takes a lot of trouble to dispose the lid in a trash box before eating the contents of the container. According to the method of the present invention, the high-temperature resealing portion has a high peel strength, so that the lid is left sealed at the edge of the container. Therefore, after ingesting the contents, the lid and the container body can be disposed together, which is convenient.

[Example] Hereinafter, one example of the method of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a conceptual plan view when the method of the present invention is carried out, and FIG. 2 is a graph showing the relationship between heat seal temperature and peel strength.

As shown in FIG. 1, a lid member 20 is provided on the upper end surface 10 of the rim of the container.
And heat seal the entire outer peripheral edge of the lid material at a temperature of about 120 ° C, and then about 180 ° C for a part of the outer peripheral edge of the lid material.
Heat seal again at the temperature. In FIG. 1, the mesh-shaped portion 30 is a portion that has been heat-sealed again at a high temperature in addition to the low-temperature heat-sealing.
Is a portion which has not been heat-sealed at a low temperature. A gripping piece 50 is provided on a part of the outer periphery of the lid material so that the lid material can be easily peeled off. The gripping piece 50 is not heat-sealed.

The range of the low-temperature / high-temperature double seal portion on the outer peripheral edge of the lid material can be arbitrarily selected or set according to the application of the container. This range may be intermittent rather than continuous as shown.

The material and shape of the molding container are not particularly limited. Therefore, it is possible to use containers of materials and shapes well known to those skilled in the art such as soft drinks, chilled desserts, cup ramen, etc.

The same applies to the material and shape of the lid material itself. Depending on the purpose of the container body, the material of the lid material to be combined with it,
Laminated structures and shapes will be apparent to those skilled in the art without needing explanation.

The hot melt adhesive that is extrusion coated on the outer periphery of the lid material is, for example, ethylene vinyl acetate (EVA) copolymer, special polyophine resin, polyethylene / EVA / tackfire ternary resin, styrene resin, etc. It is included as the main component. This kind of adhesive is commercially available, for example, by Dainippon Ink and Chemicals (Dicktherm EL), Toyo Soda Kogyo (Mersen M), Mitsui DuPont Chemical (CMPS), Hirodyne Industry (Hirodine 7500 series) and the like.

The adhesive used in the method of the present invention preferably has a large rate of change in peel strength depending on the heat sealing temperature.

The peel strength range for obtaining a practically appropriate easy-open property cannot be unconditionally determined because factors such as the lid material composition, rigidity, thickness and container shape, strength are involved, but generally about 500 It is said to be about -1500g / 15mm width. Therefore, the first heat seal is about 500-800
It is preferable to carry out at a temperature at which a peel strength of about g / 15 mm width is obtained, and the second heat sealing is carried out at a temperature at which a peel strength of about 1500 g / 15 mm width or more is obtained.

It is preferable that the first low-temperature heat-sealed portion is separated at the interface and the second high-temperature heat-sealed portion is not separated unless cohesive failure occurs.

The amount and method of applying the adhesive applied to the outer peripheral edge of the lid material are well known to those skilled in the art.

FIG. 2 is a graph showing the relationship between heat seal temperature and peel strength.

In the experiment, PET (12
(μm) / PE (20 μm) / EVA adhesive (20 μm), which was heat-sealed. The first heat sealing was performed at a sealing pressure of 4 kg / cm ² , a sealing time of 1 second, and a temperature of 10
The temperature was changed from 0 ° C to 120 ° C. The second heat seal was performed under the same conditions except that the temperature was changed from 130 ° C to 200 ° C. The peel strength was measured by peeling at 180 ° and the peeling speed was 300 mm / min.

As is clear from the results shown in FIG. 2, when the second heat-sealing treatment is performed in addition to the first heat-sealing treatment, it is about twice as much as when the heat-sealing treatment is performed only once at low temperature. The above peel strength is achieved.

In the second heat-sealing process, if not only the heat-sealing temperature but also the sealing pressure and the sealing time are set to be higher than those in the first-time processing conditions, even higher peel strength will be obtained.

Therefore, the achieved peel strength can be changed by the combination of (a) the material and configuration of the container body, (b) the material and configuration of the lid material, and (c) the material and configuration of the adhesive. The desired optimum peel strength can be easily determined by those skilled in the art by repeating experiments under predetermined conditions.

[Effects of the Invention] As described above, in the method of the present invention, the entire periphery of the outer peripheral edge of the lid material is heat-sealed to the rim of the container at a low temperature, and then a part of the outer peripheral edge of the lid material is heated again at a high temperature. Consisting of sealing.

When treated in this manner, the peel strength of the portion reheat-sealed at a high temperature is significantly higher than the peel strength of the low-temperature heat-sealed portion. In this way, both the easy-open property and the high sealing property can be achieved at the same time.

As a practical matter, in some cases, only a portion of the lid needs to be detached from the edge of the container. For example, in the case of a soft drink container, a space for inserting a straw may be provided. Thus, it is possible to eliminate the dangerous use of cutting the tip of the straw sharply and piercing it with the lid and inserting it into the container. Further, in the case of a cup ramen container, only the portion necessary for pouring hot water can be peeled off. This is because the lid is replaced after pouring boiling water.

Furthermore, if the lid is completely separated from the container, it takes a lot of trouble to dispose the lid in a trash box before eating the contents of the container. According to the method of the present invention, the high-temperature resealing portion has a high peel strength, so that the lid is left sealed at the edge of the container. Therefore, after ingesting the contents, the lid can be disposed together with the container body, which is excellent in convenience.

[Brief description of drawings]

FIG. 1 is a conceptual plan view when the method of the present invention is carried out, and FIG. 2 is a graph showing the relationship between heat seal temperature and peel strength. 10 …… Container edge, 20 …… Lid, 30 …… Double seal,
40 …… Single seal part, 50 …… Grip piece

Claims (4)

[Claims] 1. When the lid is heat-sealed to the upper end surface of the rim portion of the molding container, the lid is placed on the upper end surface, and the entire outer peripheral edge of the lid from the upper surface of the lid is placed along the upper end surface portion. Partial lid double sealing method, characterized in that the circumference is heat-sealed at a relatively low temperature and then a part of the outer peripheral edge of the lid is heat-sealed again at a temperature higher than the temperature at the time of the first heat-sealing. . 2. The first heat sealing temperature is about 100.degree.
The partial lid of claim 1 wherein the temperature is in the range of about 120 and the second heat seal temperature is in the range of about 130 ° C to about 200 ° C. Double sealing method. 3. The peel strength of the first heat-sealed portion is about 500 g / 15 mm width or more and less than 1500 g / 15 mm width.
The partial lid double sealing method according to claim 1 or 2, wherein the peel strength of the second heat-sealed portion is about 1500 g / 15 mm width or more. 4. The peel strength of the first heat-sealed portion is in the range of about 500 g / 15 mm width to 800 g / 15 mm width, and the peel strength of the second heat-sealed portion is about 1500 g / 15 mm width or more. The partial lid double sealing method according to claim 3, wherein