JPH0459220B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an easily openable sealed container, and more specifically, the present invention relates to an easily openable sealed container, and more specifically, the container has a peel strength from the center side that is high enough to withstand retort sterilization, etc. The present invention also relates to an easily openable sealed container that can be opened reliably and stably by hand from the outside of the container. (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 and 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, Plastics, Vol. 38, No. 5, Page 65 (1987) provided a heat-sealable inner material layer on the entire inner surface of the container body, and In addition to providing an easily peelable seal between the two layers and a tight seal between the inner material layer and the lid, a score is provided to cut the inner material layer closer to the center than the heat-sealed part, and heat is applied from the center to the outside. A heat-sealed container has already been proposed that has a seal strength of 2.3 kg/15 mm or more and can be easily opened 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 used. For example, in laminated containers with an intermediate layer of metal foil such as steel foil, there is a risk of rust occurring in the score area. It becomes unusable at this point. Further, in order to provide the score, the area of the container flange inevitably increases, which is undesirable from the viewpoints of an increase in the amount of container material used, an increase in the bulk of the package, and poor appearance. Additionally, in general, in easily openable heat-sealed containers, simply having an easily peelable seal on the heat-sealed portion does not necessarily mean that the unsealing will be easy. It is necessary to make sure that stress is concentrated at the opening start portion of the easily peelable seal portion. Therefore, it is an object of the present invention that the peeling or breaking strength from the center side of the container is, for example, 2.3 kg/15
By being large (more than mm width), it can withstand the increase in internal pressure during retort sterilization, and the peel strength from the outside of the container is maintained at the heat seal strength for easy opening. To provide an easily openable sealed container in which stress is concentrated on an easily peelable seal part so that manual opening can be performed reliably and stably. Another object of the present invention is to provide an easily openable sealed container in which the above-mentioned anisotropy of peel strength is achieved without marking the container or container lid with a score. (Means for Solving the Problems) According to the present invention, a cup-shaped container having a heat-sealing flange and a lid are sealed by heat-sealing, and at least the unsealing start portion of the sealed portion is It has an intermediate material inserted so as to protrude outward from the heat-sealing flat part of the flange, and there is an easily peelable seal between the intermediate material and the flange, and a tight seal between the intermediate material and the lid. Yes, the inner edge of the easily peelable seal part is located inside the container than the inner edge of the tight seal part, and the outer edge of the tight seal part is located outside the heat-sealing flat part of the flange at the opening start position. Provided is an easily openable sealed container characterized by being located at. (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. Sealing is performed between the flange 1 and the lid 3 by heat sealing, and in the present invention, an intermediate member 4 is provided in a specific positional relationship at least at the opening start portion of this sealing portion. That is, the flange 1 has a heat-sealing flat part 5, and the intermediate member 4 is provided so as to protrude outward from the outer peripheral edge 6 of the heat-sealing flat part 5. In the specific example shown in FIG. 1, a tight seal portion 7 is formed between the intermediate material 4 and the lid 3, while an easily peelable seal is formed between the intermediate material 4 and the flange flat portion 5. 8 is formed. The inner edge 9 of the easily peelable seal part 8 is located inside the container than the inner edge 10 of the tight seal part 7, and the outer edge 12 of the easily peelable seal part 8 is tight at the opening start position 11. It is located further inside the container than the outer edge 13 of the seal portion 7 . In FIG. 2, which shows a state in which a peeling force is applied from the inside to this sealing part, the inner edge 14 of the intermediate member 4 is in close contact with the flange 1 or the container beyond the flange 1, and The inner edge 9 of the easily peelable seal part 8 is located inside the container than the inner edge 10 of the tight seal part 7, so that the peeling force or breaking force P from the inside is tight. It acts on the seal portion 7 and can provide a large peeling or breaking strength of, for example, 2.3 kg/15 mm width or more. On the other hand, in FIG. 3, which shows a state in which a peeling force P' from the outside is applied to the opening start position 11 of the sealed portion, when the end 15 of the lid 3 is grasped and pulled upward, the intermediate material 4 is removed. The outer edge 13 of the tight seal portion 7 protrudes outward from the flange flat portion 5 and is formed between the intermediate material 4 and the lid 3.
is located further outward than the outer edge 12 of the easily peelable seal portion 8, so that the end of the intermediate material 4 is also attached to the lid 3.
The peeling force P' is concentrated on the outer edge 12 of the easily peelable seal part 8, and opening by hand can be performed reliably and stably, and the peeling strength from the outside is also 2 kg/15 mm or less. Can be in a range of easy-to-open seals. In the heat sealing structure shown in FIG. 1, substantially the entire container flange 1 is covered with the heat sealing flat portion 5
The intermediate material 4 is provided so as to protrude outward from the outer end 6, but as shown in FIG. The same can be done by forming the intermediate member 4 and the outer circumferential extension part 16 provided outwardly and downwardly through the step 15, and by not performing heat sealing between the intermediate material 4 and the outer circumferential extension part 16. effect is achieved. In the sealed container of the present invention, the intermediate material 4 and the container 2
Heat sealing is performed in advance during the container manufacturing process prior to filling the container with the contents. On the other hand, heat sealing between the intermediate material 4 and the lid 3 is performed in a process different from the container manufacturing process after filling the contents. Generally, when heat-sealing after filling the contents, it is often difficult to strictly control the position and area of the heat-seal, but in the present invention, by adopting the above-mentioned configuration, it is possible to sufficiently heat-seal after filling. As long as a suitable heat-sealing area is secured, a predetermined difference can be achieved between the peeling or breaking strength from the center of the container and the peeling strength from the outside of the container without inscribing a score on the container or lid. becomes possible. (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 easily peelable seal portion on the other side, it is necessary to Take advantage of the difference in heat sealing strength. For example, if the intermediate material is a polypropylene film and the inner surface of the lid or container is made of polypropylene, a tight seal will be formed.
Further, 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 easily peelable 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 the inner surface of the lid and the inner surface of the container are both made of polypropylene, if the intermediate material is made of polypropylene, tight sealing and blending are required on the polypropylene layer side. An easily peelable seal will be formed on the layer side. 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.
This coating film is provided on the inner surface of the lid or container, and by adjusting the amount of acid-modified olefin resin dispersed in polyethylene oxide, a tight seal is formed on one side of the polyolefin film and an easily peelable seal is formed on the other side. be able to. 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 easily peelable seal part and the inner and outer edges of the tight seal part can be controlled by any means. Most simply, the positions of the inner and outer edges can be controlled by controlling the shape and position of the heat seal head when heat sealing the intermediate material to the lid or container flange. Alternatively, a non-adhesive coated film defining the inner and outer edges of the heat-sealed portion may be applied to the flange surface, lid, etc. by printing, coating, vapor deposition, welding, or other known thin film forming techniques. It can be applied to the inner surface or intermediate material to regulate the position of the inner and outer edges of the heat-sealed portion. However, in the present invention, by providing the intermediate material so as to protrude outward from the flat part for heat sealing, the positions of the outer edge of the easily peelable sealing part and the outer edge of the tight sealing part are adjusted during heat sealing. Regulation is generally unnecessary. Further, as shown in FIG. 5, the intermediate material is provided so as to have a portion 17 that protrudes inward from the sealing flat portion 5 of the flange, and this inward protruding portion 1 of the intermediate material is provided.
When 7 is heat-sealed to the container side, there is an advantage that there is no need to restrict the position of the inner edge of the tight seal portion. The container body and the 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 have at least the inner surface made of an intermediate material and a resin having heat-sealing properties, such as, but not limited to, low-medium-high-density polyethylene, isotactic polypropylene, Propylene-ethylene copolymer, ethylene-vinyl acetate copolymer,
Olefin resins such as olefin resins graft-modified with ethylenically unsaturated carboxylic acids or their anhydrides; polyamide or copolyamide resins with relatively low melting points or low softening points; polyesters or copolyamide resins with relatively low melting points or low softening points; Polyester resin; made of polycarbonate resin, etc. 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, steel, tin plate, etc. as an intermediate layer. Further, it may be a so-called well-known metal container in which these metal materials are coated with a resin known per se such as a thermosetting resin or a thermoplastic resin. 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. It goes without saying that the heat-sealing structure in which an intermediate material is inserted in the present invention is provided over the entire sealed portion between the container and the lid, but in the heat-sealing structure, once peeling of a certain length is performed, It should be understood that since subsequent peeling progresses relatively easily, it may be provided only at the portion of the sealing portion where peeling begins. (Effects of the Invention) According to the present invention, the intermediate material is provided in a specific protruding relationship at least at the opening start portion of the sealed portion between the flanged container and the lid, and a tight seal is formed between the intermediate material and the lid. By forming an easy-to-open, peelable seal between the container and the flange, the peel or break strength from the center of the container can be compared with the peel strength from the outside of the container without marking the container or lid. It has become possible to provide a predetermined difference between the seals, and when starting to open the seal, it has become possible to concentrate the peeling force on the edge of the easily peelable seal and start peeling reliably and stably. The invention is illustrated by the following example. (Examples) Example 1 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, and on the aluminum side of the base material, a 50 μm unstretched polypropylene film is laminated with urethane adhesive as a heat seal layer. . Cup-shaped container: 75μm surface treated steel foil with 40μm on one side and 40μm on the other side.
A 70μm unstretched polypropylene film is laminated with a urethane adhesive, and this laminate is deep drawn so that the 70μm film side becomes the heat sealing surface.The outer diameter has a heat sealing flange with a width of 5mm. 78mm round container. Intermediate material A two-layer coextruded film consisting of a 45μm polypropylene layer (layer A) and a 5μm blend layer (layer B) made of a 30% by weight blend of linear low-density polyethylene with ethylene-propylene random copolymer. . A sealed container of the type shown in FIG. 1 was produced using these lid materials, cup-shaped containers, and intermediate materials.
The intermediate material was provided around the entire circumference of the heat sealing surface, and the intermediate material was allowed to protrude 3 mm outward from the flange. Heat-sealing involves first heat-sealing (easy-peel sealing) between the molded container and the intermediate material (layer B), then filling approximately 90% of the total volume with water, and then sealing the intermediate material (layer A) and the lid. It was sealed by heat sealing (tight sealing). The easily peelable seal was applied to the entire heat-sealed surface by interposing a 12 μm biaxially stretched polyethylene terephthalate film between the intermediate material and the heat-seal head. In addition, the shape and position of the heat seal head is regulated so that the distance between the easily peelable seal part and the inner edge of the tight seal part is 2 mm, and the outer edge of the tight seal part is on the outside of the flange. I did it. Table 1 shows the heat sealing conditions for the easily peelable seal and the tight seal portion. The peel strength and unsealing strength of the thus obtained sealed and filled container were measured using a tensile tester after retort sterilization at 120°C for 50 minutes. To measure peel strength, cut out a 15 mm wide strip perpendicular to the direction of the heat seal, place the lid side of the strip between the top chuck and the side wall of the cup between the bottom chuck, and then cut the strip 300 mm wide.
I pulled it up and down at a speed of 1 minute. In addition, the opening strength can be determined by fixing the container on the cross head at a 45° angle, and placing the grip for opening the lid on the upper chuck (the angle between the top of the container and the grip on the lid is 45°). This was done by pulling it up and down at a speed of 300 mm/min. Table 1 shows the measurement results of the peeling or breaking strength from the inside of the container, the peeling strength from the outside at the opening start point, and the opening strength. Example 2 The specifications of the lid material, cup-shaped container, and intermediate material used in Example 2 are shown below. Lid material Same as the lid material used in Example 1. Cup-shaped container: A 40 μm unstretched polypropylene film on one side of a 75 μm surface-treated steel foil, and a 5 μm layer made of a 45 μm polypropylene layer and a 30% by weight blend of linear low density polyethylene in ethylene-propylene random copolymer on the other side. A two-layer coextruded film consisting of a blend layer of
This laminate was deep-drawn so that the coextruded film side became the heat sealing surface, and the resulting product had a width of 5 mm.
A round container with an outer diameter of 78 mm and a heat sealing flange. Intermediate material: 50μm unstretched 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. Furthermore, peel strength (or breaking strength) and unsealing strength were measured in the same manner as in Example 1. Heat sealing conditions and 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 One side of a 50 μm aluminum foil is surface treated to improve paint film adhesion, and a 5 μm thick epoxy/phenol paint containing 10 PHR of maleic anhydride modified polypropylene is applied to that surface as a heat seal layer. The paint is baked on. Cup-shaped container: One side of a 0.2 mm tin plate is coated with epoxy/phenol paint, and the other side is coated with epoxy/phenol paint containing 3 PHR of maleic anhydride-modified polypropylene to a thickness of 2 μm and 5 μm, respectively. It was obtained by deep drawing a coated plate so that the coated film side containing modified polypropylene became the heat-sealing surface. A round container with an outer diameter of 78 mm and a heat sealing flange with a width of 5 mm. Intermediate material: 50μm unstretched 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. Furthermore, peel strength (or breaking strength) and unsealing strength were measured in the same manner as in Example 1. Heat sealing conditions and measurement results are shown in Table 1. 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 terephthalate film, 15 μm biaxially stretched nylon-6 film, and 20 μm soft aluminum foil are laminated with urethane adhesive on the aluminum side of the base material.
15μm maleic anhydride modified polypropylene layer,
35μm blend of 20% by weight linear low density polyethylene with ethylene-propylene random copolymer
A coextrusion coating of blended layers. Cup-shaped container A square container with a side length of 80 mm and a 3 mm wide heat-sealing flange, obtained by vacuum forming a 2 mm polypropylene sheet. Intermediate material Same as the intermediate material used in Example 1. A hermetically sealed container of the type shown in FIG. 5 was produced in the same manner as in Example 1 using these lid materials, cup-shaped containers, and intermediate materials. However, as shown in FIG. 7, the intermediate material was provided only at one corner of the container (the opening start point). Peel strength (or breaking strength) and unsealing strength were measured in the same manner as in Example 1. Heat sealing conditions and measurement results are shown in Table 1. Example 5 The specifications of the lid material, cup-shaped container, and intermediate material used in Example 5 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, 50 μm polyethylene terephthalate, polyethylene terephthalate isophthalate, polybutylene terephthalate, etc. are applied as a heat seal layer. A four-component blend film of isophthalate and ionomer is laminated with a urethane adhesive. Cup-shaped container 0.2mm polyethylene terephthalate layer (layer A)
A coextruded sheet consisting of a 0.8 mm polyethylene terephthalate layer (layer B) blended with a nucleating agent is vacuum-formed so that layer A becomes the heat-sealing surface, and heat-treated after forming. Ta,
Outer diameter 78 with 6mm width heat sealing flange
mm round container. Intermediate material One layer is a 60μm blend layer (C layer) consisting of polyethylene terephthalate, polyethylene terephthalate isophthalate, polybutylene terephthalate isophthalate and ionomer,
A two-layer coextruded film in which one layer is a 10 μm blend layer (D layer) consisting of polyethylene terephthalate/isophthalate, polybutylene terephthalate/isophthalate, and ionomer. 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. Note that the intermediate material was heat-sealed with the cup-shaped container on the D-layer side and with the lid material on the C-layer side. Furthermore, peel strength (or breaking strength) and unsealing strength were measured in the same manner as in Example 1. Heat sealing conditions and measurement results are shown in Table 1. Example 6 The specifications of the lid material, cup-shaped container, and intermediate material used in Example 6 are shown below. Lid material Same as the lid material used in Example 5. Cup-shaped container Epoxy/phenol paint is applied to one side of 0.13 mm aluminum foil, which has been surface treated on both sides to improve paint film adhesion, and epoxy/phenol paint is applied to the other side.
A heat-sealing flange with a width of 6 mm was obtained by coil-coating urea-based paint to a thickness of 5 μm and 3 μm, respectively, and deep-drawing this foil so that the epoxy/phenol-based coating side was the heat-sealing surface. A square container with a side length of 80 mm. Intermediate material Same as the intermediate material used in Example 5. 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. Note that the intermediate material was heat-sealed with the cup-shaped container on the D-layer side and with the lid material on the C-layer side. Furthermore, peel strength (or breaking strength) and unsealing strength were measured in the same manner as in Example 1. Heat sealing conditions and measurement results are shown in Table 1. Comparative Example Using the lid material and cup-shaped container used in Example 4, a sealed and filled container was produced without inserting an intermediate material into the heat-sealed portion. Peel strength and unsealing strength were measured in the same manner as in Example 1. Heat sealing conditions and measurement results are shown in Table 1. An object of the present invention is to provide an easy-to-open sealed container that can withstand an increase in internal pressure during retort sterilization, is easy to open, and can be opened reliably and stably. In Examples 1 to 6, the peeling or breaking strength from the inside of the container is 2.3 kg/15 mm width or more, which is strong enough to withstand the increase in internal pressure during retort sterilization, and the peeling strength from the outside is around 1 kg/15 mm width, making it easy to open. It has become a sticker. In addition, the opening strength was less than 2 kg, and when I actually held the opening part in my hand and tried peeling it off, it was easy to open. However, in the comparative example, the peel strength was
Although it is over 2.3Kg/15mm width, the opening strength is 4Kg.
Due to the above, it was difficult to open the package by hand. 【table】

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional structural view illustrating an easily openable sealed container of the present invention, FIG. 2 is a cross-sectional view showing a state in which a peeling force is applied from the inside to the sealed portion of the container, and FIG. The figure is a sectional view showing a state in which a peeling force from the outside is applied to the opening start part of the container, and FIGS. 4, 5, and 6 are sectional views showing examples of application of the intermediate material. , FIG. 7 is a perspective view illustrating a state in which the intermediate material is applied only to the unsealing start part. Reference number 1 is the heat sealing flange, 2 is the container body, 3 is the lid, 4 is the intermediate material, 7 is the tight seal part, 8 is the easy-to-peel seal part, 9 is the inner edge of the easy-to-open seal part, Reference numeral 10 indicates the inner edge of the tight seal portion, 11 indicates the opening start portion, 12 indicates the outer edge of the easy-to-open seal portion, and 13 indicates the outer edge of the tight seal portion.

Claims (1)

[Scope of Claims] 1. A container in which a cup-shaped container having a heat-sealing flange and a lid are sealed by heat-sealing, wherein at least the opening start portion of the sealed portion is closer than the flat portion of the flange for heat-sealing. It has an intermediate material inserted so as to protrude outward, and there is an easily peelable seal between the intermediate material and the flange, and a tight seal between the intermediate material and the lid, and the inside of the easily peelable seal part. The edge is located further inside the container than the inner edge of the tight seal portion, and the outer edge of the tight seal portion is located outside the heat sealing flat portion of the flange at the opening start position. Easy-to-open sealed container. 2. The sealed container according to item 1, wherein the intermediate material is provided so as to protrude outward from the outer peripheral end of the flange at least at the opening start portion of the sealed portion. 3 The flange of the cup-shaped container has a flat part for heat sealing and an outer peripheral extension provided outward and downward from the flat part with a difference, and a heat seal is provided between the intermediate material and the outer peripheral extension. The first thing that has not been done is
Sealed container as described in section. 4. The sealed container according to item 1, wherein the intermediate material is provided so as to protrude inward from the heat-sealing flat portion of the flange, and this protruding portion of the intermediate material is heat-sealed to the container side.