JPH0451432B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to an easily openable sealed food container, and more specifically, the present invention relates to an easily openable sealed food container, and more specifically, a container that has a peel strength from the center side of the container that is high enough to withstand, for example, retort sterilization. The present invention relates to an easily openable sealed food container whose peel strength from the outside is maintained at an easily openable seal strength such that it can be opened by hand. (Prior art) Conventionally, heat-sealed packaging bodies have been widely used in many fields such as food packaging, and those that can be peeled off at the heat-sealed interface are also widely used as easy-to-open or peelable heat-sealed lids. It is used. For heat-sealed packages whose contents have been subjected to retort sterilization, the sealing strength of the heat-sealed part must be at least 2.3 kg/15mm width, and the sealing strength between the container body and lid must be When this value is reached, it becomes difficult to manually peel off the heat-sealed interface between the two. To solve this problem, a heat-sealable inner material layer is provided on the inner surface of the container body, and the inner layer and the inner layer are easily peelable, and this inner surface is placed closer to the center than the heat-sealed part. A heat-sealed container has already been proposed in which a score is provided to cut the material layer, and the heat-sealing strength from the center to the outside is 2.3 kg/15 mm or more, while making it easy to open from the outside. (Problems to be Solved by the Invention) The above-mentioned easy-to-open heat-sealed container is significant in that it imparts easy-to-open properties to the package while maintaining sealing strength of 2.3 kg/15 mm or more. The problem is that there are restrictions on the structure and manufacturing of the container, such as the need to perform score processing on the container. In addition, in order to score the inside of the peripheral area for heat sealing, there are restrictions on the container material that can be used, and the area of the container flange inevitably becomes larger, which increases the amount of container material used and reduces the packaging material. It is also unfavorable from the viewpoint of increased bulk and appearance characteristics. Therefore, an object of the present invention is to have a high peel strength from the center side of the container, for example, 2.3 kg/15 mm width or more, so that it can withstand increased internal pressure during retort sterilization, and To provide an easily openable sealed food container whose peel strength from the outside is maintained at an easy open heat seal strength. Another object of the present invention is to provide an easily openable sealed food container in which the above-mentioned peel strength anisotropy is achieved without marking the container or container lid with a score. (Means for Solving the Problems) According to the present invention, in a container in which opposing portions of a plurality of container materials are sealed by heat sealing, at least an unsealing start portion of the sealed portions is formed of the plurality of container materials. and an intermediate material inserted between them, and the intermediate material and one of the plurality of container materials have a tight seal, and the intermediate material and the other of the plurality of container materials have an easy-to-open seal. Yes, the inner edge of the easy-to-open seal part is located closer to the center than the inner edge of the tight-seal part, and the outer edge of the easy-to-open seal part is tight at the opening start position. There is provided an easily openable sealed food container characterized in that the seal portion is located closer to the center than the outer peripheral edge. (Function) In FIG. 1 showing an example of the container of the present invention, this container is composed of a container body 2 having a heat-sealing flange 1 and a lid 3. An intermediate member 4 is provided between the flange 1 and the lid 3. 1st
In the specific example shown in the figure, a tight seal 5 is formed between the intermediate material 4 and the lid 3, and on the other hand,
An easily openable seal 6 is formed between the intermediate material 4 and the flange 1. The inner peripheral edge 7 of the easy-to-open seal portion 6 is located closer to the center than the inner peripheral edge 8 of the tight seal portion 5, and the easy-to-open seal portion 6 is located closer to the center than the inner peripheral edge 8 of the tight seal portion 5.
The outer peripheral edge 10 of the tight seal portion 5 is located closer to the center than the outer peripheral edge 11 of the tight seal portion 5 . In FIG. 2, which shows a state in which a peeling force is applied from the inside to this sealing part, the inner circumferential edge 12 of the intermediate member 4 is in close contact with the flange 1, and the easily-openable sealing part 6 is located closer to the center than the inner edge 8 of the tight seal portion 5, and therefore, the peeling force or destructive force P from the inside acts on the tight seal portion 5. For example,
A large peeling or breaking strength of 2.3Kg/15mm width or more can be obtained. On the other hand, in FIG. 3, which shows a state in which a peeling force from the outside is applied to the unsealing starting part 9 of this sealing part, when the end part 13 of the lid 3 is grasped and pulled upward, the easy-to-open seal part 6 Since the outer peripheral edge 10 of the tight seal part 5 is located closer to the center than the outer peripheral edge 11 of the tight seal part 5, the peeling force P'
For example, it has a peel strength of 2 kg/15 mm width or less, and can be easily peeled and opened by hand. In the heat-sealed structure shown in FIG. 1, the intermediate material 4 remains on the lid side after opening, and the flange portion 1 has a clean appearance, but as shown in FIG. It is also possible to have a structure in which the seal part 6 is provided upside down and remains on the cup side after the intermediate material 4 is opened. The intermediate material 4 may be provided around the entire circumference of the sealed portion, but may also be provided only at the opening start portion 9. When unsealing, the opening strength is greatest at the sealed portion where the peeling width is widest, and generally at the opening start portion 9. Therefore, even if the seal strength between the container 2 and the lid 3 is strong, for example, 2.3 to 3 kg/15 mm width,
By inserting the intermediate material 4 into the unsealing starting part 9, making one side a tight seal 5 and the other an easy-to-open seal 6 through the intermediate material, and regulating their positions, the same effect as described above can be obtained. Since the maximum value of the opening strength is reduced, opening becomes easier. According to the present invention, the tight seal portion and the easy-to-open seal portion are provided on both sides of the intermediate member 4, and by regulating the positions of the inner and outer edges of the container or It is possible to provide a predetermined difference between the peel strength from the center of the container and the peel strength from the outside of the container without imprinting a score on the lid. (Description of Preferred Embodiments) In the present invention, in order to provide a tight seal on one side of the intermediate material and form an easy-to-open seal portion on the other side, it is necessary to Utilizing the difference in heat sealing strength. For example, if the intermediate material is a polypropylene film, a tight seal will be formed if the inner surface of the lid or the inner surface of the container is made of polypropylene. Furthermore, if the inner surface of the lid or the inner surface of the container is formed of a blend of polypropylene and other polymers such as polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene rubber, etc., an easy-to-open seal will be formed. In addition, if the intermediate material is made of a laminated structure of a polypropylene layer and the blend layer, and both the inner surface of the lid and the inner surface of the container are made of polypropylene, a tight seal is attached to the polypropylene layer side and an easy-to-open seal is attached to the blend layer side. will be formed. These examples also apply to heat-sealable resins such as polyethylene, polyester, and polyamide. It is also known that polyolefine films have heat-sealing properties for certain coatings. That is, polyolefin film exhibits excellent heat-sealing properties compared to coating films in which oxidized polyethylene or acid-modified olefin resin is dispersed.
By providing this coating on the inner surface of the lid or container and adjusting the amount of dispersed polyethylene oxide or acid-modified olefin resin, a tight seal is formed on one side of the polyolefin film and an easy-to-open seal is formed on the other side. Can be done. This trend is reflected in polyester, which exhibits paint and heat sealability.
This also applies to resins such as polyamide. The positions of the inner and outer edges of the easy-to-open seal portion and the inner and outer edges of the tight seal portion can be controlled by any means. The simplest method is to control the position of the inner and outer edges by controlling the shape and position of the heat seal bar when heat sealing the intermediate material to the lid or container flange. can. Alternatively, a non-adhesive film may be printed to define the inner and outer edges of the heat-sealed portion.
The position of the inner and outer edges of the heat-sealed portion can be controlled by coating, vapor deposition, welding, or other known thin film forming techniques on the flange surface, inner surface of the lid, or intermediate material. The container body and lid may be made of any container-forming material known per se, such as resin, metal, paper, glass, ceramic, or a laminate thereof. Suitable container bodies and lids are made of a resin having heat-sealing properties at least on the inner surface, such as low-medium-high-density polyethylene, isotactic polypropylene, propylene-ethylene copolymer, ethylene-vinyl acetate copolymer. Olefin resins such as olefin resins graft-modified with polymerized or ethylenically unsaturated carboxylic acids or their anhydrides; polyamide or copolyamide resins with relatively low melting points or low softening points; polyesters with relatively low melting points or low softening points. or copolyester resin. The container body may be a container formed from these resins alone, or may be a laminated container including a metal foil such as aluminum foil, steel foil, or tin foil as an intermediate layer. The lid body can be made of metal foil such as aluminum foil, tin foil, steel foil, or tin foil, or thermoplastic resin film such as biaxially stretched polyethylene terephthalate film, biaxially stretched nylon film, or polycarbonate film.
The base material may be a variety of papers or a laminate thereof, and the above-mentioned heat-sealable resin layer may be laminated thereon as an inner surface material. The intermediate material is a film made of one or more layers of the heat-sealable resin described above, and its thickness must be at least resistant to breakage when the package is opened, and generally has a thickness of 15 to 1000 μm, particularly 30 to 100 μm. Preferably within this range. The present invention is particularly useful for applications in which the contents are sterilized by retort or boiling, or by hot filling.In this case, from the standpoint of heat resistance, the inner material of the container and lid may be made of polypropylene resin. is common. Particularly suitable intermediate materials for this application are those with a thickness of 15 to 1000 μm, especially 30 to 1000 μm.
A 90:10 mixture of a polypropylene film in the range of 100 μm, a propylene-ethylene copolymer with a thickness of 1 to 100 μm, especially 3 to 50 μm, and polyethylene.
Mention may be made of intermediate materials consisting of 50 to 50 blend layers. Although the present invention has been described above with respect to a sealed container consisting of a cup-shaped container and a lid, the present invention can also be applied to a container formed by heat-sealing two pieces of pouch constituent material around the circumference. can. In FIG. 5 showing an example of this container, pouch constituent materials 2', 2' are heat-sealed via an intermediate material 4, with a tight seal 5 on one side of the intermediate material and an easy-open seal 6 on the other side. to form. The positional relationship of the edges of these seal parts is the same as that shown in FIG. The intermediate material 4 may be provided all around the pouch, or may be provided only in the portion of the pouch that is to be opened. (Effects of the Invention) According to the present invention, the tight seal portion and the easy-to-open seal portion are provided on both sides through an intermediate material, and the positions of the inner peripheral edge and outer peripheral edge thereof are regulated. This makes it possible to provide a predetermined difference between the peel strength from the center of the container and the peel strength from the outside of the container without engraving a score on the container or lid, thus making it possible to manually It is possible to provide an easily openable sealed food container. Example 1 The specifications of the lid material, cup-shaped container, and intermediate material used in Example 1 are shown below. Lid material 12 μm biaxially stretched polyethylene terephthalate film and 9 μm soft aluminum foil are laminated with urethane adhesive. On the aluminum side of the base material, a 70 μm unstretched isotactic polypropylene film is laminated with urethane adhesive as a sealing layer. What I did. Cup-shaped container: 75μm surface treated steel foil with 40μm on one side and 40μm on the other side.
A heat-sealing flange with a width of 6 mm is made by laminating 70 μm unstretched isotactic polypropylene film with a urethane adhesive and deep drawing the laminate so that the 70 μm unstretched isotactic polypropylene film side becomes the sealing surface. Round container with. Intermediate material: 50 μm isotactic polypropylene layer,
2 manufactured using a T-die consisting of a 5 μm blend layer made of a 30% by weight blend of linear low density polyethylene into an ethylene/propylene random copolymer.
Layered coextruded film. A sealed container of the type shown in FIG. 1 was produced using these lid materials, cup-shaped containers, and intermediate materials. Heat sealing was performed by first creating an easy-to-open seal between the molded container and the intermediate material, filling the container with water to approximately 90% of the total volume, and then tightly sealing the intermediate material and the lid. Table 1 shows the sealing conditions for the easy-open seal and tight seal. Further, the positions of the inner and outer edges of the easy-to-open seal portion and the inner and outer edges of the tight seal portion were controlled by regulating the shape and position of the heat seal bar. The seal widths of the easy-open seal part and tight seal part are 3 mm and 2 mm, respectively.
mm, the distance between the inner edges was 2 mm, and the distance between the outer edges was 0.5 mm. The peel strength of the thus obtained sealed and filled container was measured before and after retort sterilization at 120°C for 50 minutes. To measure peel strength, cut a 15 mm wide strip perpendicular to the direction of the seal, and place the lid side of the strip into the upper chuck and the side wall of the cup between the lower chuck.
This was done by pulling it up and down at a speed of 300 mm/min.
Table 1 shows the measurement results from the inside of the container and the measurement results from the outside at the beginning of opening. Example 2 A sealed container of the type shown in FIG. 4 was produced using the same lid material, cup-shaped container, and intermediate material as in Example 1. Heat sealing was performed by first tightly sealing the molded container and the intermediate material, filling it with water to approximately 90% of the total volume, and then performing an easy-to-open seal with the intermediate material to seal the container. Table 1 shows the sealing conditions for the easy-open seal and tight seal. The positions of the inner and outer edges of the easy-to-open seal and the inner and outer edges of the tight seal are controlled by vacuum deposition on both sides of the intermediate material. An adhesive aluminum film was formed. In addition, Example 1
Similarly, the seal widths of the easy-to-open seal portion and the tight seal portion were 3 mm and 2 mm, respectively, the distance between the inner edges was 2 mm, and the distance between the outer edges was 0.5 mm. The peel strength of the thus obtained sealed and filled container was measured in the same manner as in Example 1. The measurement results are shown in Table 1. Example 3 The specifications of the lid material, cup-shaped container, and intermediate material used in Example 3 are shown below. Lid material Same as the lid material used in Example 1. Cup-shaped container: 75 μm surface-treated steel foil with 40 μm unstretched isotactic polypropylene film on one side, and linear low-density polyethylene on 50 μm isotactic polypropylene layer and ethylene-propylene random copolymer on the other side. 30% by weight blended
A two-layer coextruded film made using a T-die consisting of a 5 μm blend layer is laminated with a urethane adhesive, and this laminate is deep drawn so that the blend layer on the coextruded film side serves as the sealing surface. A round container with a heat-sealing flange with a width of 6 mm. Intermediate material: 50μm unstretched isotactic polypropylene film. A hermetically sealed container of the type shown in FIG. 1 was produced in the same manner as in Example 1 using these lid materials, cup-shaped containers, and intermediate materials. Further, peel strength measurements were also carried out in the same manner as in Example 1. Table 1 shows the heat sealing conditions and peel strength measurement results. Example 4 The specifications of the lid material, cup-shaped container, and intermediate material used in Example 4 are shown below. Lid material: 12 μm biaxially stretched polyethylene reterephthalate film and 9 μm soft aluminum foil are laminated with urethane adhesive on the aluminum side of the base material.
A two-layer coextruded film made using a T-die is blended with a 50 μm isotactic polypropylene layer and a 5 μm blend layer made of a 30% by weight blend of linear low-density polyethylene and ethylene-propylene random copolymer. The layers were laminated using a urethane adhesive so that the layers would serve as sealing layers. Cup-shaped container Similar to the cup-shaped container used in Example 1. Intermediate material: 50μm unstretched isotactic polypropylene film. A hermetically sealed container of the type shown in FIG. 4 was produced in the same manner as in Example 2 using these lid materials, cup-shaped containers, and intermediate materials. Further, peel strength measurement was performed in the same manner as in Example 1. Table 1 shows the heat sealing conditions and peel strength measurement results. Example 5 The specifications of the lid material, cup-shaped container, and intermediate material used in Example 5 are shown below. Lid material One side of a 50 μm aluminum foil is surface treated to improve paint film adhesion, and a sealing layer of 5 μm thick epoxy/phenol paint containing 10 PHR of maleic anhydride modified polypropylene is applied to that surface. Painted and baked on. Cup-shaped container A 0.2 mm tin plate is coated with epoxy/phenol paint on one side and an epoxy/phenol paint containing 7 PHR of maleic anhydride-modified polypropylene on the other side to a thickness of 2 μm and 5 μm, respectively. A round container made by deep drawing a painted plate so that the coating side containing modified polypropylene becomes the sealing surface, and forming a heat sealing flange with a width of 6 mm. Intermediate material: 50μm unstretched isotactic polypropylene film. A hermetically sealed container of the type shown in FIG. 1 was produced in the same manner as in Example 1 using these lid materials, cup-shaped containers, and intermediate materials. Further, peel strength measurement was also carried out in the same manner as in Example 1. Table 1 shows the heat sealing conditions and peel strength measurement results. Example 6 The specifications of the lid material, cup-shaped container, and intermediate material used in Example 6 are shown below. Lid material One side of 50μm aluminum foil has been surface-treated to improve paint film adhesion, and 5μm thick epoxy/phenol paint has been baked onto that surface as a sealing layer. Cup-shaped container A 20 μm three-component blend film of polyethylene terephthalate isophthalate, polybutylene terephthalate isophthalate, and ionomer is thermally bonded to one side of a 0.5 mm polyethylene terephthalate sheet containing a nucleating agent using a hot roll. A square container with a heat-sealing flange of 6 mm in width, which is pressure-formed so that the blend film side becomes the sealing surface and heat-treated after molding. Intermediate material An 80μm four-component blend film made of a blend of polyethylene terephthalate, polyethylene terephthalate/isophthalate, polybutylene terephthalate/isophthalate, and ionomer. A hermetically sealed container of the type shown in FIG. 4 was produced in the same manner as in Example 2 using these lid materials, cup-shaped containers, and intermediate materials. Further, peel strength measurement was performed in the same manner as in Example 1. Table 1 shows the heat sealing conditions and peel strength measurement results. Example 7 A 12 μm biaxially stretched polyethylene terephthalate film and a 9 μm soft aluminum foil were laminated with a urethane adhesive, and a sealing layer was applied to the aluminum side of the base material, and a 70 μm unstretched isotactic polypropylene film was laminated with a urethane adhesive. Using the packaging material laminated in and the intermediate material used in Example 1,
A pouch shown in FIG. 5 was produced. For heat sealing, use an impulse sealer.
The tight seal side was done first, and the easy-open seal side was done later. The seal widths of the easy-open seal portion and the tight seal portion were 5 mm, and the easy-open seal was shifted 2.5 mm toward the inside of the pouch with respect to the tight seal so as to have the positional relationship shown in FIG. 6a. A strip of 15 mm width was cut out from the opening starting point of the pouch thus prepared, perpendicular to the sealing direction, and the T-peel strength was measured at a pulling speed of 300 mm/min. Table 2 shows the measurement results from the inside and outside of the pouch. Comparative Examples 1 and 2 In Example 7, the easy-open seal was shifted 2.5 mm to the inside of the pouch compared to the Tight Seal, and the positional relationship was as shown in Figure 6a. In the same position as shown in Example 7 (Comparative Example 1), or by shifting the easy-open seal by 2.5 mm to the outside of the pouch compared to the tight seal as shown in Figure 6c (Comparative Example 2), in the same manner as in Example 7. A pouch was made using the method. The T-peel strength was measured in the same manner as in Example 7. The measurement results are shown in Table 2. An object of the present invention is to provide a sealed food container that can withstand increased internal pressure during retort sterilization and can be easily opened from the outside of the container.As can be seen from Tables 1 and 2, In Examples 1 to 7, the peel strength from the inside of the container was 2.3Kg/15
It is strong enough to withstand increased internal pressure during retort sterilization and has a peel strength of 2 kg/mm or more from the outside.
It is less than 15mm wide and has an easy-to-open seal. When the containers of Examples 1 to 7 were actually peeled off by holding the opening start part in the hand, they were easily opened.
However, in Comparative Examples 1 and 2, the desired effect of the present invention was not observed, and in Comparative Example 2, the package could not be opened by hand.

【table】

【table】

[Brief explanation of the drawing]

1, 4, and 5 are diagrams each showing a cross-sectional structure of an example of the easy-to-open sealed container of the present invention, and FIG. 2 shows the sealed container example shown in FIG. FIG. 3 is a sectional view showing a state in which a peeling force from the inside is applied to the container, and FIG. FIG. 6 is a cross-sectional view illustrating the positional relationship between the easy-open seal portion and the tight seal portion in the sealed containers of Example 7 and Comparative Examples 1 and 2. Reference number 1 is the heat-sealing flange, 2 is the container body, 3 is the lid, 4 is the intermediate material, 5 is the tight seal part, 6 is the easy-to-open seal part, and 7 is the inner edge of the easy-to-open seal part. , 8 is the inner peripheral edge of the tight seal portion, 10 is the outer peripheral edge of the easy-to-open seal portion, 11
indicates the outer peripheral edge of the tight seal portion.

Claims (1)

[Scope of Claims] 1. A container in which opposing portions of a plurality of container materials are sealed by heat sealing, wherein at least the opening initiation portion of the sealing portions is connected to the plurality of container materials and an intermediate material inserted therebetween. The intermediate material and one of the plurality of container materials are a tight seal, and the other of the intermediate material and the plurality of container materials is an easy-to-open seal. The circumferential edge is located closer to the center than the inner circumferential edge of the tight seal portion, and the outer circumferential edge of the easy-to-open seal portion is located closer to the center than the outer circumferential edge of the tight seal portion at the opening start position. An easy-to-open sealed food container characterized by being located on the center side. 2. One of the container materials is a cup-shaped container equipped with a heat-sealing flange, the other container material is a lid, there is an easy-to-open seal between the cup-shaped container and the intermediate layer, and the lid and the intermediate layer are 2. The food container according to claim 1, wherein there is a tight seal between the container and the container. 3. The food container according to claim 1, wherein the plurality of container materials are two pieces of pouch-constituting materials.