JPH11240546A - Packaging container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable fitting structure by providing a fitting projection part provided on a container body or a lid body of a structure where valley parts are continuously formed to adjacent projections to solve problems of the releasing property and the fluctuation of the coefficient of post-shrinkage. SOLUTION: Fitting projections 5 are provided on four corner parts of a lid body 2 of a container body 1. The fitting projections 5 which are corrugated in section and projected inwardly in the radial direction of the corner parts, are engaged with outwardly projecting edges 7 of the corner parts of the container body. Valley parts 6 of the corrugation are located outwardly in the radial direction of the corner parts from the projecting edges 7. Thus, a gap 10 is present between the valley parts 6 and the projecting edges 7, and the engagement between the container body 1 and the lid body 2 becomes slightly loosened. The size is affordable even when irregular post-shrinkage is generated in the container body and the lid body, the fitting projections are formed high with sufficient hooking to obtain the stable fitting. In addition, the fitting projections and the valley parts are alternately formed, and no defective releasing property is generated, and no resin powder is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a packaging container. More particularly, the present invention relates to a packaging container having a fitting structure for covering a container body such as a one-way food packaging container manufactured by thermoforming a synthetic resin sheet and fitting a corner of the container.

[0002]

2. Description of the Related Art Conventionally, a lid is put on a main body of a packaging container thermoformed from a synthetic resin sheet and fitted to each other by fitting the lid to the entire periphery or corner of the container main body or the lid or both. This is achieved by forming convex portions and concave portions that enable the formation.

[0003] Such a packaging container in which a container body and a lid can be fitted is mass-produced and consumed as a food packaging container for displaying and selling side dishes and bento boxes at convenience stores and supermarkets. It is desired that manufacturers of prepared dishes and bento boxes can easily and reliably cover the container while fitting the lid to the container body, and for consumers who have purchased this prepared dish or bento, open the lid of the container. In such a case, it is desired to be able to easily and safely open the package.

When manufacturing these food packaging containers, in order to meet these demands as much as possible, the container main body and the lid are formed with corresponding projections and depressions having a fitting function corresponding to each other.
In many cases, a mechanism is provided such that the cover main body is covered with a lid and then pressed down from above so that the fittable portions of the container main body and the lid fit into each other and fit.

As a specific example, FIG. 4 shows an example of a conventional packaging container. FIG. 3A is an enlarged plan view of the corner portion, and FIG. 3B is a sectional view taken along line BB of FIG. In FIG. 4, the flange portion 43 of the substantially rectangular container lid 42 is shown.
A convex portion 45 is provided on the inside of the corner of the peripheral side hanging portion 46 hanging down the entire periphery of the container, and is fitted to a substantially horizontal protruding edge 47 formed at the corresponding corner of the container body. . Although not shown in the figure, a concave groove is provided over the entire periphery of the peripheral edge of the substantially rectangular container lid, so that it can be fitted to the corresponding ridge provided on the peripheral portion of the corresponding container main body. There are also things.

[0006] In the case of the above-described lid body, after being formed by thermoforming, the formed projections are firmly engaged with the mold, making it difficult to easily and efficiently release the mold from the mold. In many cases, in order to obtain good release characteristics, it is often necessary to set the convex portions lower than a desired height.

[0007]

Due to the characteristics of the synthetic resin, a packaging container thermoformed from a synthetic resin sheet may shrink in a few hours to several tens of hours after being thermoformed and may be slightly deformed. (Hereinafter referred to as "post-shrinkage"). This is a factor that determines the stretching characteristics such as freeze orientation formed during the production of the synthetic resin sheet to be used, such as the type of raw resin used, the heating condition during thermoforming, and the cooling timing and cooling time after shaping. Depending on the conditions, post-shrinkage occurs in different directions and to different degrees.

Although the shrinkage of the molded product is extremely small as a whole, the influence on the fitting strength is large. More specifically, for example, when the degree of rear shrinkage of the lid is large, the fitting becomes tight. When the cover is fitted to the container body, the operation for fitting may be difficult. On the other hand, if the lid does not shrink after a predetermined amount, the fitting may be too loose and a sufficient fitting strength may not be obtained.

[0009] As described above, the occurrence of excessively strong or weak fitting due to the fitting strength being too strong or too weak is not preferable for a food packaging container in which food is put in and sold for display. For example, when food is stored and made into a product, a lunch box using the container is manufactured and displayed and sold, or when a consumer purchases a lunch box or the like and opens it, the lid accidentally comes off, On the contrary, problems such as difficulty in opening the lid occur. In addition, in order to prevent the above-mentioned problems due to the post-shrinkage, the lid is formed to be relatively large, and when the convex portion for performing the fitting is formed to be high to increase the fittable range,
The convex portion fitted from the molding die hardly comes off, which may cause problems such as trouble in releasing work, breakage or damage to a part of the lid during releasing, and the like. Further, in mass production, there is a case where it is necessary to take measures to prevent the molded portion of the mold from being rubbed with the molded product at the time of mold release, thereby preventing resin powder from being generated and adhering to the molded product.

The problems described above can be summarized as follows.

[0011] 1. If a fitting structure (deepening the fitting portion) for stable fitting is to be provided, it is necessary to take measures to prevent the releasability from being deteriorated or to prevent the generation of resin powder during mass production. And sometimes.

2. The container body and the lid shrink with time after thermoforming, and the fitting of the container body and the lid may become unstable due to the variation in the amount of shrinkage.

3. If the fitting is made too deep, the fitting between the container body and the lid becomes too strong, and it is necessary to apply a strong force to open the lid. Therefore, the lid comes off at once at the moment of opening. The reaction may cause a problem such as spilling the food in the container.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a stable fitting structure that solves problems caused by the releasability of a molded article and fluctuations in post-shrinkage shrinkage. It is intended to provide a packaging container.

[0015]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies and found that a convex portion for generating a fitting function is formed at a corner of a container body or at a corner of a lid. It was found that the above problems could be solved by providing a structure in which the projections with the intermittent projections interposed were provided, and the present invention was completed.

That is, the packaging container according to the present invention is a packaging container in which a lid is fitted and fixed to a container body thermoformed from a synthetic resin sheet, and a fitting projection is provided on the container body or the lid. The fitting projection is formed of a plurality of projections which are continuously formed by forming a valley between adjacent projections.

According to the present invention, the container body and the lid are formed with a margin enough to prevent the fitting from being too tight even if the post-contraction unevenness occurs, and the container body and the lid are subjected to the post-shrinkage. The above problem is caused by forming a convex portion formed high enough to have sufficient catch even if unevenness is formed as a continuous protrusion at a corner portion of, for example, a rectangular lid molded from a synthetic resin sheet. The point can be solved. Then, the planar shape of the packaging container can be substantially formed into a polygon such as a triangle to a pentagon, a circle, or the like. In the case of a circular shape, the fitting projections may be divided and provided in several places, or may be provided continuously over the entire circumference of the circle.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The packaging container of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a view showing one example of a packaging container according to the present invention, and FIG.
(B) is a sectional view taken along line AA. 2A is an enlarged plan view of a corner portion of FIG. 1A, and FIG. 2B is a cross-sectional view taken along line BB of FIG. FIG. 3 shows another example of the packaging container of the present invention. FIG. 3A is an enlarged plan view of the corner portion, and FIG. 3B is a sectional view taken along line BB of FIG.

1 to 3, reference numeral 1 denotes a container body, 2
Is a lid, 5 is a fitting projection, and 6 is a valley. When the fitting projection 5 is pressed from above, the tip of the flange portion 4 of the container body 1 (hereinafter, referred to as “projecting edge”) as shown in FIG.
7, so that the lid 2 is fitted to the container body 1.

In the embodiment shown in the drawings, fitting projections 5 are provided at four corners of a lid 2 to be put on the container body 1. The fitting projection is formed in a cross-sectional waveform in the case of the figure, and the fitting projection 5 projecting inward in the radial direction of the corner is engaged with the outwardly protruding edge 7 of the corner of the container body. It is. In FIG. 2, the trough 6 of the waveform is located radially outward of the corner from the protruding edge 7. Therefore, there is a gap 10 between the valley 6 and the protruding edge 7,
The engagement between the container body 1 and the lid 2 is slightly loosened. FIG. 3 shows an embodiment in which the valley 6 is configured such that the outwardly projecting edges 7 are located at substantially the same position. There is no gap between the two, and the container body 1 and the lid 2 are compared with the configuration of FIG. Engagement is slightly stronger.

The fitting projection 5 of the packaging container according to the present invention.
Has a plurality of continuous projections formed at least at each corner 9 of the container body 1 or the lid 2, a valley 6 is provided between adjacent projections 5, and the number of the valleys 6 is 0.5. /cm
-4 / cm, preferably 1.5 / 3 to 3 / cm, more preferably 2 / 2.5 to 2.5 / cm. When the number of the valleys 6 is less than 0.5 / cm, it is difficult to sufficiently obtain the effects of providing the valleys between the fitting projections, such as releasability, covering, and easy opening. 4 copies / c
If m is exceeded, the thickness of the tip of the projection becomes thin and it becomes difficult to form a projection of sufficient height, or the projections become too fine and the projection cannot be molded according to the shape of the mold, which is preferable. Absent.

The shape of the fitting projection is not particularly limited, and the tip of the projection may be flat, hemispherical, conical, pyramidal, similar or a combination of a plurality thereof.

The appropriate value of the height of the projection differs depending on the shape and size of the container.
Preferably, a range of 0.8 mm or more and 2.0 mm or less is a range of a practically appropriate value. If the height of the projections exceeds 3.5 mm, it is difficult to release the mold after the completion of molding, and if it is smaller than 0.3 mm, it becomes difficult to realize stable fitting.

The valleys 6 provided between the consecutively provided projections are usually basically located at the same position as the base where the projections 5 rise, but may be provided at a position higher than the base or as necessary. It may be a deeper position. Here, the base portion is the outer surface of the peripheral hanging portion 8 of the lid serving as a reference for fitting with the protruding edge of the container body. When the deepest part of the valley is provided at a position higher than the base of the protrusion, the fitting strength tends to increase, but at the same time, the releasability after molding tends to decrease. Conversely, the deepest part of the valley When the value of is decreased, the releasability after molding tends to be good, but the fitting strength tends to decrease. In this case, by making the deepest portion of the valley lower than the base of the protrusion, more excellent releasability and ease of opening can be obtained.

The packaging container according to the present invention uses a thermoplastic synthetic resin as a main material and has a thickness of, for example, 0.15 mm or more and 1.8 mm.
The following non-foaming or expansion ratio is 5 times or less, preferably 3 times
Extrusion molding of a single-layer or laminated synthetic resin sheet having a thickness of not more than twice or laminating the above-mentioned sheet with various films, and subjecting this sheet to a container body and a lid by a thermoforming method such as vacuum forming, pressure forming, and vacuum forming. Shape the body. As the synthetic resin to be used, those used for the production of one-way food packaging containers, which are currently manufactured in large quantities, can be used without any problem. An agent, a coloring agent, or the like, which has been mixed, or a material that causes low foaming of 5 times or less can be used as appropriate.

Examples of synthetic resin materials that can be used include:
It is possible to use a thermoplastic resin in which polystyrene, polypropylene, polyester, polycarbonate, etc. are used alone or in a mixture of a plurality of them in an arbitrary ratio, and it is also possible to use a compound raw material that imparts rubber properties for adjusting the resin properties. is there. Of course, as long as it is a resin raw material that can be extruded into a sheet and meets the conditions for forming the sheet into a food packaging container by the above-mentioned thermoforming method, the crystallinity, branching properties of the polymer, and other resin properties are not particularly limited. It is also optional to use additives and the like generally used for adjusting and improving various properties currently used in the production of similar food packaging containers.

Further, a molded article using a sheet produced from a raw material synthetic resin mixed with a filler may be used. As the usable filler, an inorganic type or an organic type may be used. It can be appropriately used without limitation as long as the production of the container is not hindered.

As for the foaming agent, a foaming agent such as a chemical foaming agent and a filling gas foaming agent can be arbitrarily added within a range where the final firing rate of the product is 5 times or less. Here, if the foaming ratio exceeds 5 times, a required molded shape of the fitting projection may not be obtained, or a stable height of the protrusion may not be obtained. Better.

The thickness of a sheet for producing a molded product is as follows:
It is preferably from 0.15 mm to 1.8 mm, preferably from 0.2 mm to 1.0 mm, more preferably from 0.25 mm to 0.5 mm. If the thickness of the sheet is less than 0.15 mm, it will be difficult to maintain the basic strength of the container body or lid, which is usually used as a one-way food packaging container, and at the same time, the whole and partial deformation of the molded product will occur more than necessary. To make it easier
Necessary fitting strength cannot be obtained, and there is no point in providing a fitting structure. On the other hand, if the thickness exceeds 1.8 mm, the amount of resin used and the strength of the container body and the lid, which exceed the necessity of a normal one-way food packaging container, will be exhibited, which not only wastes resources but also increases the thickness. This makes it difficult for the shape of the fitting projection to appear accurately, making it difficult to obtain the stability of the fitting strength, and also tends to cause problems such as difficulty in opening because the fitting strength becomes too strong. I will.

Although the case where the lid is placed on the container body has been described above, the fitting mechanism of the present invention can also be applied to the case where the lid fits inside the outermost peripheral edge of the main body. . Further, the packaging container of the present invention may be provided with a linear convex portion on a peripheral hanging portion other than the corner portion of the lid to assist in fitting the lid as conventionally performed.

[0031]

Examples [Examples] Extruded inorganic powder-filled polypropylene sheet (CT sheet, manufactured by Chuo Chemical Co., Ltd.)
A 0.5 mm thick) is formed by a vacuum forming method to form a substantially rectangular food packaging container body 1 (230 m long) as shown in FIG.
m, width 200 mm, depth 24 mm, corner radius 18.5 mm). The lid 2 fitted to the packaging container body 1 was formed by a pressure forming method using a biaxially stretched polystyrene resin sheet (Dick Sheet SB, 0.25 mm thick, manufactured by Dainippon Ink Co., Ltd.). A fitting protrusion 5 having a truncated cone shape over a width of 45 mm is provided on a peripheral hanging portion 8 of a corner portion 9 (FIG. 1) of the lid 2.
(FIG. 2), that is, (9 pieces / 4.5 cm =) 2 pieces / cm.

The height of the fitting projection 5 is 0.9 mm, and the height of the projection is 0.5 mm in the opposite direction to the projection, that is, 0.5 mm outward in the radial direction. The difference was 1.4 mm. The mold releasability at the time of molding was observed while 20 sets of the container body and the lid were formed, and after the molding was left at room temperature for 48 hours, the fitting strength was measured.

The measuring method is as follows. The tip of a U-shaped bracket connected to a universal testing machine (Shimadzu Autograph AGS 500S) is hooked on the corner of the lid fitted to the container body with the bottom fixed, and pulled upward. (Pulling speed: 50mm / mi
n.), the force (peak value) when the lid comes off (unit: g)
Is the fitting strength. The results are shown in Tables 1 and 2.

When the lid is released from the mold during molding, it can be performed extremely well without the fitting projections being caught by the mold, and there is no breakage line or scratch due to a poor release. Did not occur. From this result, it is presumed that the generation of resin powder hardly occurs even during mass production of products. Also, the variation in the fitting strength at which the fitting is released from the numerical values in Table 1 above shows a low value in the average value of the fitting strength, and a significantly lower value in the unbiased variance value as compared with the comparative example. And good fitting characteristics were shown.

COMPARATIVE EXAMPLE Instead of the fitting projections 5 shown in FIGS. 1 to 3, a conventional fitting projection 45 having a cross section similar to a kamaboko type as shown in FIG. 4 is provided at the corner of the lid. Was. 45mm in length in the circumferential direction of the corner of the fitting projection, 0.6m in height
m. Except for this, the same observation and measurement were performed as in Example 1 described above. As a result, in releasing the lid from the mold, when the fitting convex portion comes off from the mold, an impact sound accompanying strong release was generated, and a part of the lid corner was not generated even though the folding line was generated. The occurrence of fine scratches was observed. In addition, the variation in the fitting strength at which the fitting was released showed a significantly higher value in the unbiased variance value than in the example. The measurement results are shown in Tables 1 and 2 together with the above examples.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

Since the packaging container of the present invention has the above-described structure, the problems of the conventional packaging container can be solved and the following effects can be obtained.

1. Even if the post-contraction unevenness occurs in the container body and the lid, the container is provided with a size margin so that the fitting is not too tight, and the fitting projection is formed higher than before, so that the post-shrinkage is reduced. Even if it occurs, it can have a sufficient hook, so that a stable fitting can be obtained.

2. Since the fitting projections and the valleys are alternately formed, no releasability failure occurs and no resin powder is generated.

3. It is easy to fix and open, and the food in the container is not spilled.

[Brief description of the drawings]

FIG. 1 (a) is a plan view showing an example of a packaging container according to the present invention, and FIG. 1 (b) is a sectional view taken along line AA of FIG. 1 (a).

2A is an enlarged plan view of a corner portion in FIG. 1A, and FIG. 2B is a cross-sectional view taken along a line BB in FIG.

3A is an enlarged plan view of a corner portion of another example of the packaging container according to the present invention, and FIG. 3B is a sectional view taken along line BB of FIG.

4A is an enlarged plan view of a corner portion of an example of a conventional packaging container, and FIG. 4B is a cross-sectional view taken along line BB of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 41 Container main body 2, 42 Lid body 3, 43 Flange part of lid body 4, 44 Flange part of container main body 5 Fitting projection 6 Valley part 7, 47 Protrusion edge 8, 46 Peripheral side hanging part 9 Corner part 10 Gap 45 convex

Claims (1)

[Claims] 1. A packaging container for fitting and fixing a lid to a container body thermoformed from a synthetic resin sheet, wherein the container body or the lid is provided with a fitting projection, and the fitting projection is A packaging container comprising a plurality of projections formed in series with a valley formed between adjacent projections.