JPH04292931A - Stock sheet for easily openable container, easily openable container and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the strength of a container at its thin wall part from lowering without impairing its easily-openable property by a method wherein the linear thin wall part is produced by vacuum-forming or air pressure forming plastic sheet, to the specified depth of the thickness of which continuous cut is made by laser machining. CONSTITUTION:A round mirror-shaped rice-cake ('KAGAMI-MOCHI' in Japanese) container 1 has a container body part 3 prepared by forming plastic sheet- like matter into the shape of the round mirror-shaped rice-cake having swollen parts at its middle and near its lower end and a flange 5, at the bottom of which a plastic bottom sheet 4 is sealed by heat sealing, at its lower end part. In the above-mentioned container, linear thin wall part 6 is provided on the outer surface of the container body part 3 and, in addition, a notched part 7 is provided in the flange 5 so as to facilitate the opening of sealing. At the formation of the thin wall part 6, continuous cut is made by laser machining to the depth of 50% or less of the thickness of the plastic sheet so as to be turned into the linear thin wall part, when the sheet is vacuum-formed or air pressure formed in the form of the container main body 3.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a raw material sheet for a plastic container, a plastic container, and a method for manufacturing the same by vacuum forming or pressure forming, and in particular to a vacuum forming method that is easy to open and has excellent strength. Or, it relates to an original fabric sheet for a plastic container, a plastic container, and a manufacturing method thereof by air pressure forming.

0002

BACKGROUND OF THE INVENTION Containers made from vacuum-formed or pressure-formed plastic sheets have been widely used as containers for various foods, confectioneries, and the like.

[0003] An example of a container made by vacuum forming or pressure forming such a plastic sheet is a container for wrapping kagami mochi.

[0004] The packaged kagami-mochi, as shown in FIG. 9, is a kagami-mochi container 1 made of plastic filled with kagami-mochi 2.

This packaged kagami-mochi uses a container body 3 made by vacuum forming a plastic sheet into the shape of a kagami-mochi with an open bottom.The container body 3 is inverted, filled with mochi 2, and then the bottom is made of plastic. The container was sealed with a sealing sheet (bottom sheet) 4 and then heat-treated. Polypropylene or the like is used for such a container body 3 from the viewpoint of adhesion to the rice cake 2. Moreover, the polypropylene used is of considerable thickness and hardness in order to ensure shape retention and gas barrier properties. In addition, as the bottom sheet 4,
Similar to the container body 3, various plastics are used.

In this packaged kagami mochi, the mochi 2 is removed from the container body 3.
To take out the rice cake, the rice cake 2 is usually cut along with the container body 3 using a knife or the like, and after the cutting, the container body 3 and the rice cake 2 are separated. This is because the body part 3 and the mochi are in close contact with each other.
This is because it is not easy to take out the rice cake just by peeling off the bottom sheet 4. However, when cutting the mochi 2 together with the container body 3 using a knife or the like, since the container body 3 has a certain degree of hardness and wall thickness as described above, a large pressing force is first applied with the knife or the like. Moreover, since the outer surface of the container body 3 is smooth, there is a problem that the knife tends to slip easily and cause injury.

[0007] Thus, vacuum-formed containers are difficult to open. Therefore, by creating linear thin-walled parts or incisions in the original fabric sheet using a cutter or roller, etc., and then performing vacuum forming or pressure forming, a linear thin-walled part is created in the container so that it can be torn by hand. is proposed.

However, when making cuts in plastic sheets using a cutter, roller, etc., it is difficult to control the depth of the cuts, and thin sections obtained by vacuum forming or pressure forming are difficult to control. However, it was found that they do not necessarily have sufficient ease of opening. On the other hand, if the thin-walled part is made quite thin in order to make it easier to open, the container will not only tend to crack from this part during vacuum forming or pressure forming or when filling the container with contents, but also cracks will occur in the event of impact. The problem arises that it is easy to enter.

[0009] Accordingly, an object of the present invention is to provide a raw sheet for an easy-to-open container that has easy-to-open properties and excellent strength, an easy-to-open container, and a method for manufacturing the same.

0010

[Means for Solving the Problems] In view of the above problems, as a result of intensive research, the present inventors have developed a container by vacuum forming or pressure forming a raw sheet made by forming notches in a plastic sheet by laser processing. It was discovered that the cut is a linear thin part, and even if the depth of the cut is shallow, it has sufficient ease of opening, and furthermore, the strength of the container in the thin part is improved, and the present invention I came up with this idea.

[0011] That is, in the original sheet for easy-open containers of the present invention, which is formed by providing a notch in a plastic sheet, the notch is formed by laser processing, and the depth of the notch is equal to the thickness of the sheet. less than 50% of
The sheet is vacuum-formed or pressure-formed so that the notch becomes a linear thin-walled portion.

[0012] Furthermore, the easy-open container of the present invention, in which a linear thin wall portion is provided by vacuum forming or pressure forming a raw plastic sheet having notches, has the notches formed by laser processing, The depth of the cut is 50% or less of the thickness of the sheet.

Furthermore, in the method of manufacturing an easy-to-open container having a linear thin wall portion according to the present invention, continuous incisions are made by laser processing at a depth of 50% or less of the thickness of the plastic sheet, and the incisions are made in a vacuum. The thin linear portion is formed by molding or pressure forming.

[0014]

[Operation] In the present invention, a container is produced by vacuum forming or pressure forming an original fabric sheet, which is formed by forming notches on a plastic sheet by laser processing. The container obtained in this manner has a thin section with linear cuts, and even if the depth of the cut is shallow, the ease of opening is not impaired, and the strength of the container in the thin section is improved. There is.

[0015] The reason why such an effect is obtained is not necessarily clear, but in the periphery of the cut made by laser processing, the plastic that is the material is momentarily exposed to high temperature, so it is thermally denatured. This is thought to be because it can be easily torn by hand. Therefore, the incision suitable for manual tearing can be made shallow, and the strength of the container at the thin wall portion is improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. 1 and 2 are a side view and a front view of a kagami-mochi container, which is a typical example of the easy-to-open container of the present invention.

This kagami-mochi container 1 consists of a container body 3 and a bottom sheet 4. The container body 3 is formed by vacuum forming or pressure forming a sheet-like plastic material into a kagami-mochi shape with constrictions near the center and lower end, and a flange 5 is formed at the lower end.

The bottom sheet 4 is also made of plastic and is heat-sealed to the flange 5 to seal the container body 3 (not shown in FIG. 2). The bottom sheet 4 is made of a material that is easy to peel from the container body 3, so that the sealing sheet (bottom sheet) 4 can be easily peeled off from the container body 3 when taking out the rice cake 2. It is set as. In such a kagami-mochi container,
A linear thin wall portion 6 is formed on the outer surface of the mirror cake-shaped portion of the container body portion 3. Furthermore, the flange 5 is provided with a notch 7 to make opening easier.

In this embodiment, the thin wall portion 6 is formed on the outer surface of the container body 3, but it may be formed on the inner surface of the container body. Good too.

A method for manufacturing such a kagami-mochi container will be explained. In the present invention, the plastic sheet forming the easy-to-open container is not particularly limited, and single plastics or laminates of plastics can be used. As a single plastic, polypropylene is preferable, and as a laminate, a layered structure such as polypropylene/polyvinyl alcohol/polypropylene is preferable. In addition, when using a kagami mochi container as in this example, higher fatty acids such as stearic acid can be added to the plastic resin for the purpose of improving the peelability from the mochi. When the above-mentioned sheet-like material is made of a simple plastic, higher fatty acids may be added to the plastic, and when the sheet-like material is a laminated sheet, the innermost layer (
Higher fatty acids such as stearic acid may be added to the resin layer that will be the surface that comes into contact with the rice cake. When adding higher fatty acids such as stearic acid, the amount added is preferably 0.1 to 5% by weight.

[0021] The thickness of the sheet may be appropriately set depending on the size, shape, weight, etc. of the articles to be filled in the container. For example, when using a kagami-mochi container as in this embodiment, the weight of the mochi filled in the kagami-mochi container body 3 is usually 160 g or more.
Since the weight is about 8 kg, it is preferable to use one with a diameter of about 550 μm to 1.5 mm. Sheet thickness is 55
If it is less than 0 μm, it will be difficult to maintain the kagami-mochi shape when filling the rice cake, and it will also be difficult to have gas barrier properties, and if it exceeds 1.5 mm, vacuum forming or pressure forming will be difficult.

In the present invention, cuts are provided in such a sheet by laser processing. FIG. 3 shows the sheet after the incisions were formed. In FIG. 3, a cut 31 is provided approximately in the center of the original fabric sheet 30.

[0023] Examples of the laser for the laser processing include a carbon dioxide laser, an argon ion laser, a YAG laser, etc., but a carbon dioxide laser is preferable in terms of output and the like. In order to form such a cut using a laser, a laser beam may be used to scan a desired position on the plastic sheet. Note that scanning may be performed by moving the laser head while keeping the sheet fixed, or by moving the sheet conversely.

FIG. 4 shows an enlarged view of an example of a cut made by such laser processing. As shown in FIG. 4, the incision made by laser processing is formed in a linear shape by a continuous series of fine point-like recesses 40. This is because the output of the laser beam changes periodically, and the connection state of the recesses 40 differs depending on the moving speed of the sheet. It is not necessary that the recesses 40 are completely connected, and the incisions made by this laser processing may be made intermittently as long as they are close to each other as shown in FIG. The linear thin-walled portion obtained from the incision made by such laser processing has sufficient ease of opening.

The diameter of the dot-like recesses 40 (corresponding to the width of the cut) is 50 to 150 μm, and the depth is 50% or less, preferably 35%, of the thickness of the sheet material 30.
It is as follows. Note that the lower limit of the depth may be such that it scratches the surface, and is particularly preferably 10% or less of the thickness. For example, when the thickness of the sheet-like material is 550 μm, the depth of the dot-like recesses is preferably about 50 to 150 μm, and when the thickness of the sheet-like material is 1.5 mm, the depth of the dot-like recesses is preferably about 50 to 150 μm. The thickness is preferably about 150 to 500 μm. Moreover, the above-mentioned cuts may be formed on one side or both sides. When forming on both sides, the depth of each cut is 3
The thickness is preferably about 25% or less of the thickness.

Further, the laser output, beam diameter, and scanning speed may be appropriately set depending on the material and thickness of the plastic bottom sheet, the depth of the cut, etc. However, as for the scanning speed, the higher the scanning speed, the larger the distance between the dotted recesses becomes, which impairs the ease of opening.

FIG. 6 shows a cross section of a sheet provided with such point-like recesses. In FIG. 6, a plastic sheet 60 is provided with point-like recesses 61, and the periphery thereof is a degenerated portion 62. When a cut is made with a cutter or roller as in a conventional kagami mochi container, if the cut is made too shallow, it becomes difficult to tear the resulting container by hand. If the portion is denatured, tearing is possible even if the incision is just enough to leave a scratch on the sheet.

Note that the incisions made by laser processing do not need to be formed across the center of the sheet material as in this embodiment, but are at least at positions where the contents (Kagami-mochi in this embodiment) can be easily taken out. The length may be any length, and may be provided halfway down the sheet to correspond to the linear thin section. Similarly, the notches do not need to be on the entire kagami-mochi container.

[0029] Such a sheet is subjected to vacuum forming or pressure forming. The vacuum forming and pressure forming methods may be any commonly used methods. For example, in the case of vacuum forming, a sheet-like material may be heated and softened using a heater or the like, and pressed against a female mold by suction from the female mold side, applying pressure if necessary, so as to form the desired shape. In addition, in the case of pressure forming, the sheet-like material is heated and softened using a heater, etc.
Pressure may be applied from the male mold side using air or the like, and molding may be performed by pressing the mold into the female mold to form the desired shape. In addition, when providing a thin-walled portion on the outer surface of the container, the incision may be made on the side that contacts the female mold.

[0030] Molding conditions vary depending on the type of plastic used, but in the case of vacuum forming, the heating temperature of the sheet is 150 to 180°C, and the degree of vacuum is 600 to 650°C.
It is preferable to set it to mmHg. In the case of air pressure forming, the sheet may be heated at a temperature of 150 to 180° C. and a pressure sufficient to deform the sheet may be applied.

In this way, the notch provided in the sheet widens in the portion stretched by vacuum forming or pressure forming the sheet material (in this example, the portion forming the kagami-mochi shape), as shown in FIG. A thin wall portion 6 as shown is formed. Further, the cut in the flange portion 5 does not widen and remains as it is. In addition, when visually inspecting the container, the above-mentioned thin-walled part is
Although it looks like a line, if you enlarge it, it is actually formed by a series of point-like recesses, and the depth (a) of the groove formed by the thin part is usually the same as that of a sheet after vacuum forming or pressure forming. It is 10 to 30% of the thickness (b) of the object.

After forming the kagami-mochi shape in this way, a notch is provided. In this way, the container body 3 as shown in FIGS. 1 and 2 can be formed. In addition, in order to make it easier to peel off the sealing sheet, which will be described later, the body of the kagami-mochi container may be processed, such as by slightly cutting off the corners of the sheet or creating creases in the corners of the sheet. good.

Furthermore, in the kagami mochi container, the linear thin wall portion 6 is generally provided on the outer surface of the container, but the thin wall portion may be provided on the inner surface. Further, in order to obtain a more pleasant opening feeling, thin-walled portions may be provided on both sides by providing notches on both sides of the sheet.

[0034] Such an easy-to-open container of the present invention usually has a sealing sheet that seals the bottom (opening). As the sealing sheet, various plastics can be used in the same manner as the sheet for the container body described above, but in particular, single-layer materials such as polypropylene and polyethylene, and laminates of these materials with polyester, aluminum foil, etc. are used. is preferable. Its thickness is preferably 70 to 100 μm. The size and shape of the sealing sheet may be such that it can completely cover at least the opening at the bottom of the container, but it is preferably approximately the same size as the sheet-like material.

[0035] Packaging can be accomplished by heat-sealing such a sealing sheet to the bottom of the container body after the contents (rice cakes in this example) have been filled.

In the easy-to-open container of the present invention, for example, the sealing sheet is first peeled off from the container body, and then the notch 7 is removed.
The rice cake 2 can be taken out by holding both sides of the rice cake by hand and pulling the container body from the notch 7 along the thin wall part 6.

Although the present invention has been described above with reference to a kagami mochi container as a typical example thereof, the present invention is not limited thereto, and the present invention is not limited thereto, but can be formed by vacuum forming or pressure forming a sheet having notches formed by laser processing. By making various shapes,
It can be a container for various fillings.

Furthermore, the shape of the bottom of the kagami mochi container does not have to be square, and can be of various shapes such as rectangle or diamond.

The present invention will be explained in more detail by the following specific examples. Example 1 A polypropylene sheet with a thickness of 0.55 mm was processed using a carbon dioxide gas laser processing machine (manufactured by Seidensha Denshi Kogyo Co., Ltd., LASUC-
4000) at an output of 25 W, and a cut with a depth of 70 μm was made approximately in the center of the sheet.

[0040] This container body sheet was placed on a frame having a kagami-mochi-shaped female mold so that the outer surface had a notch, and vacuum-formed at a heater temperature of 180°C and a reduced pressure of 650 mmHg. The cut in the sheet after molding was a linear thin section with a depth of about 80 μm. After forming the kagami-mochi shape in this way, it is shaped as shown in Figure 8 (the length of each side is 300 mm).
A kagami-mochi container body was manufactured by cutting out a square with a diameter of 1.2 mm (mm), having a notch at approximately the center of one side, and one corner cut off at an angle of approximately 45°.

Next, 550 g of mochi was placed in the body of the obtained kagami mochi container.
After cooling, the bottom of the kagami-mochi container body was heat-sealed with a laminated sheet (thickness: 80 μm) of polyester and nylon. When the bottom sheet of this packaged kagami mochi was peeled off from the corner and torn by hand from the notch, the package could be easily opened along the thin linear part.

Comparative Examples 1 and 2 A polypropylene sheet having a thickness of 0.55 mm was traversed to a depth of 0.3 mm (comparative example 1) and a depth of 0.5 mm, respectively.
A cut of 2 mm (Comparative Example 2) was made with a rotating circular blade.

Each sheet for the container body thus obtained was placed on a frame having a female die so that the notches were on the outside surface, and heated at a heater temperature of 180° C. and a reduced pressure of 650 m.
Vacuum forming was carried out at mHg. In the kagami mochi container body obtained in this way, the one in which a sheet cut with a depth of 0.3 mm was provided (Comparative Example 1) cracked in part. In addition, in the case where a cut with a depth of 0.2 mm was provided (Comparative Example 2), a linear thin part of about 0.01 mm was formed. A kagami mochi container body was manufactured from the sheet of Comparative Example 2 in the same manner as in Example 1.

[0044] Mochi 550 was added to the body of the kagami mochi container of Comparative Example 2.
After cooling, the bottom of the kagami-mochi container body was heat-sealed with a laminated sheet (thickness: 80 μm) of polyester and nylon.

When the bottom sheet of this packaged kagami-mochi was peeled off from the corner and torn by hand from the notch, several thin linear parts were found that were difficult to tear.

As is clear from Example 1 and Comparative Examples 1 and 2, the easy-to-open container of the present invention is different from the conventional container made by vacuum forming a sheet with cuts made by mechanical means such as a cutter or roller. It can be seen that even if the cut is made much shallower, it can be easily torn, and that cracks are less likely to occur in the linear thin-walled portion.

[0047]

Effects of the Invention As detailed above, the easy-open container original sheet of the present invention is obtained by forming incisions on a plastic sheet by laser processing, and the easy-open container of the present invention It is made by vacuum forming or pressure forming an original fabric sheet.

The easy-to-open container of the present invention obtained in this manner has a thin section with a linear cut, and even if the cut is shallow, the easy-to-open container does not impair the ease of opening. strength has been improved.

The easy-to-open container of the present invention is suitable for packaging items that require easy-to-open properties and strength, such as kagami mochi containers.

[Brief explanation of drawings]

FIG. 1 is a side view of a kagami mochi container according to an embodiment of the present invention.

FIG. 2 is a front view of a kagami mochi container according to an embodiment of the present invention.

FIG. 3 is a plan view of a sheet forming the body of a kagami mochi container according to an embodiment of the present invention.

FIG. 4 is an enlarged view showing an example of notches in the sheet of FIG. 3;

FIG. 5 is an enlarged view showing another example of notches.

FIG. 6 is a schematic diagram showing a cross-sectional state of a cut.

FIG. 7 is a schematic diagram showing the state of a thin portion of the sheet.

FIG. 8 is a front view of a kagami mochi container according to another embodiment of the present invention.

FIG. 9 is a longitudinal cross-sectional view showing a state in which the kagami mochi container is filled with mochi.

[Explanation of symbols]

1... Container for kagami mochi 2... Mochi 3... Container body portion 4... Bottom sheet 5... Flange portion 6... Thin wall portions 30, 60... Plastic sheet 31... Cuts 40, 61 ... Point-like recesses 62 ... Degenerated portion

Claims (6)

[Claims] 1. An original sheet for an easy-to-open container made of a plastic sheet with a notch, the notch being formed by laser processing, and the depth of the notch being equal to the thickness of the sheet. 50% or less of the original fabric sheet for easily openable containers, characterized in that the incisions become linear thin sections by vacuum forming or pressure forming the sheet. 2. An easy-to-open container in which a linear thin-walled portion is provided by vacuum forming or pressure forming a raw plastic sheet having notches, the notches being formed by laser processing, An easy-open container characterized in that the depth of the cut is 50% or less of the thickness of the sheet. 3. The easy-open container according to claim 2, wherein the easy-open container comprises a plastic sealing sheet that seals the opening of the container. 4. The easy-open container according to claim 2 or 3, wherein the plastic sheet of the container is a single layer of polypropylene or a laminate of polypropylene/polyvinyl alcohol/polypropylene. easy-to-open containers. 5. The easy-open container according to claim 2, wherein the laser processing is performed using a carbon dioxide laser. 6. A method for manufacturing an easy-to-open container having a linear thin-walled portion, the method comprising: making continuous incisions at a depth of 50% or less of the thickness of a plastic sheet by laser processing; A method for manufacturing an easy-open container, characterized in that the cut is formed into the linear thin wall portion by air pressure forming.