JP2739988B2 - Manufacturing method of easily openable sealed container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the manufacture of a sealed container in which a lid is easily opened in a container comprising a plastic cup body having a flange portion and a lid member. About the method.

[Conventional technology]

2. Description of the Related Art As a packaging container for foods, an easy-open plastic sealed container that can be easily opened is widely used.

The most common easy-open method that has been conventionally performed is to appropriately control the sealing strength with a container (for example, 600 to 1000 g / mm) by changing the composition of the resin that constitutes the sealing layer of the lid material. Peel the interface between the material and the container and open it. However, the sealing strength is easily affected by the conditions at the time of sealing, the environmental temperature, the adhesion of contents, and the like, and the strength often varies. If this variation is biased toward the weak side, there is a danger of leaking the seal,
Conversely, if it is biased toward the strong side, the peelability will be poor and it will be difficult to open. However, since seal leakage is a fatal defect, in order to avoid this phenomenon and ensure safety, it is necessary to set a high seal temperature and pressure even at the expense of easy openness. In order to improve such a problem, a method of opening the seal layer by delamination between the seal layer and an adjacent layer (for example, Japanese Patent Publication No. 50-37598).
However, there is a drawback that the seal layer does not break well in the normal sealing method and the contents are difficult to take out.

Further, a structure in which a cut is formed in a flange portion to facilitate separation of a peeling layer from an adjacent layer has been proposed (Japanese Patent Application Laid-Open Nos. 62-251363, 63-78, 63-78, 63-78).
No. 25037). However, in the case of containers having these structures, since the container periphery of the cut portion must be sealed from the outside in the manufacturing stage, there is a manufacturing problem that strict control is required for setting the position at the time of sealing. . In addition, in the method in which the sealing layer is separated from the sealing layer of the main container, the peeling needs to be started from the peripheral edge because of sealing to the peripheral edge of the flange portion. There is a drawback to receive.

As a measure to solve this point, there is an example in which a peeling start cut and a peeling stop cut are provided on a flange portion as described in JP-A-63-96060. However, there is an inconvenience in the manufacturing process that the precision of the seal position must be strictly set.

[Problems to be solved by the invention]

The inventor of the present invention has conducted intensive studies on means for solving the above-mentioned conventional problems, and has produced a simple hermetically sealed container which has no danger of leaking a seal and is stable and easy to open without being influenced by sealing conditions. As a method, a flange of specific properties and a lid material are sealed using a convex sealer so as to form a resin pool of a resin constituting a sealing layer and a resin constituting a neighboring layer on both sides of a boundary surface between a sealing portion and a non-sealing portion. (Japanese Patent Application No. 63-216227).

A method of heat-sealing the container body and the lid material with a convex sealing plate has been known for some time, and it has been recognized that there is an advantage that a stable sealing can be performed even when the contents overflow in the flange portion, In the case of opening with the interface peeling between the sealing layer of the main body and the lid material sealing layer, both seal layers undergo complicated plastic deformation in the sealing process, so the pressure resistance is improved, but there is a difficulty in receding in terms of easy opening. there were.

Although the above-mentioned prior application greatly improved the problem relating to the ease of opening, there were still points to be improved in terms of manufacturing conditions and the like.

As a result of pursuing this point, the present invention confirmed that if the press-fitting of the convex seal disc at the time of sealing is made to be a certain level or more, the resin pool formed becomes larger and the easy-opening property is further improved, and the invention was developed. It has been reached.

[Means for solving the problem]

That is, the method for producing an easily-openable sealed container provided by the present invention has a lamination strength of 300 to 2000 g / mm between a sealing layer and an adjacent layer opposed thereto, and a thickness of the sealing layer of 10 to 7
The sealing strength of the container flange portion and the lid material, which is 0μ, is not less than the lamination strength using a convex sealer, and the sealing layer and the adjacent layer at both ends of the boundary between the sealing portion and the non-sealing portion are formed of resin. In the sealing method for forming a knob-shaped resin pool, the configuration is characterized in that press-fitting is performed until the tip of the convex heat portion reaches at least the adjacent layer surface of the container flange portion.

The material of the container body used in the present invention is a multilayer sheet having at least a sealing layer and an adjacent layer opposed thereto, for example, a simple two-layer sheet in which a polyethylene resin is disposed in the sealing layer and a polypropylene resin is disposed in the adjacent layer. Alternatively, a six-layer sheet in which a saponified ethylene-vinyl acetate copolymer or a polyvinylidene chloride-based resin barrier layer, an adhesive layer, and an outermost layer of polypropylene are further disposed on the adjacent layer via an adhesive layer may be used. In some cases, other materials such as metal and paper may be laminated on the outside of the multilayer plastic sheet.

However, the multilayer sheet has a lamination strength between the seal layer and the adjacent layer of 300 to 2000 g / 25 mm (peel angle 180 °, peel strength 20
It is important to set the thickness of the seal layer in the range of 10 to 70 μm. The reason for this is that the lamination strength is less than 300 g / 25 mm, and if the sheet layer thickness is less than 10 μ, the sealing property cannot be sufficiently secured,
On the other hand, if the lamination strength exceeds 2000 g / 25 mm and the thickness of the sealing layer exceeds 70 μm, the peel strength at the time of opening the seal increases and the smooth peelability is impaired.

It is desirable that the film forming the lid material forms a seal layer of a material that easily and tightly bonds to the seal layer of the container main body, and the most preferable mode is to form the seal layer of the lid material with the seal layer of the container main body. It is to be composed of the same material. Further, the film of the cover material may be a single layer, but may be a multilayer film containing aluminum foil, polypropylene, or the like having good barrier properties.

 Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing a sealing step using a convex sealing disk. A lid 2 is placed on a flange portion 3 of a container 1 and heat sealed using a sealing disk 5 having a convex heating portion 4. The sealing board 5 is particularly capable of extruding the sealing layer and the adjacent layer resin of the container body on both sides of the boundary surface between the sealing portion and the non-sealing portion at the time of hot pressing so as to form a lumpy resin pool. There is no restriction on the shape, and an appropriate shape such as a V-shape or a U-shape can be selected. The width of the sealing disk is preferably in the range of 1 to 3 mm.Considering the pressure of a commercially available sealing device, if the pressure is less than 1 mm, the sealing pressure increases and the main body sealing layer is cut off. It is difficult to form a resin pool. Further, it is desirable that the height of the convex heating portion 4 of the sealing board is set to about 0.1 to 3.0 mm.

FIG. 2 is a sectional view showing a state at the time of sealing. The resin constituting the sealing layer 7 of the lid 2, the sealing layer 6 of the container 1, and the adjacent layer 8 near the lower surface of the pressurized surface due to the press-fitting of the convex heat portion 4 undergoes plastic deformation, and both ends of the boundary between the sealed portion and the non-sealed portion. Extruded. Further, the press-fitting of the convex heat portion 4 is further advanced until the tip T of the convex heat portion 4 reaches at least the adjacent layer surface S as shown in FIG. Due to the strong press-fitting, the swelling of the resin is further increased, and the resin pools 9, 10, 11, and 12 in the form of bumps are formed. At this time, the resin layers 13 and 14 are also formed together with the sealing layer 7 of the lid member 2.

In the seal portion, the lid 2 and the container 1 are completely in close contact with each other, and the boundary surface between the seal layer 7 of the lid and the seal layer 6 of the container shows a mixed state of resin. In this state, the sealing strength is higher than the lamination strength of the sealing layer and the adjacent layer of the container.

(Operation)

At the time of opening, when the lid 2 is turned from the peripheral edge, a force X as shown in FIG. 4 is applied, and the seal layer 7 of the lid 2 is peeled from the seal layer 6 of the container 1. When the peeling reaches the point A in FIG. 3, the sealing layer 6 of the container 1 is cut and the peeling of the sealing layer 6 and the adjacent layer 8 is transferred. At this time, the presence of the large resin reservoirs 9 and 10 at the point A exerts a counter force against the pressing force X on the seal layer 6 to assist cutting.

The separation between the seal layer 6 and the adjacent layer 8 continues to the resin pool on the container side, but in the process up to this stage, the force X functions only for the separation. Then, when peeling reaches point B in FIG. 3, force X
Acts on both sides of peeling and cutting of the seal layer 6, but most of the resin pool portions 11 and 12 are consumed as a force for tearing the seal layer 6 because the resin pool portions 11 and 12 are formed in a large knob-like shape.

The cutting and the peeling action by the distribution of the force X as described above can be finally easily opened in the state shown in FIG.

When a press-fitting condition such that the tip T of the convex heat portion does not reach the adjacent layer surface S in the sealing step is applied, the resin layer does not become large, so that the peeling force is always more dominant than the cutting and the sealing layer 6 is cut. It becomes difficult to do.

〔Example〕

High-density polyethylene (HDPE) with a total thickness of 850μ, seal layer density 0.955, melt index (MI) 5g / 10min, and polypropylene (melt index (MI) 0.5 / min) for the adjacent layer (also serving as outer layer) A two-layer seal made of PP) was formed by co-extrusion. Then, the sheet was vacuum formed to obtain a container body having an inner diameter of 70 mm, a flange outer diameter of 82 mm, and a height of 30 mm. 800μ flange thickness of this container body,
The thickness of the sealing layer was 20 μm, and the lamination strength between the sealing layer and the adjacent layer was 800 g / 25 mm.

Biaxially stretched 6-6,6Ny (ONY)
A lid made of 25μ / HDPE60μ is overlaid and a sealing plate 5 having a U-shaped convex heating part 4 is used.
Under the condition of cm ² , heat sealing was performed by press-fitting until the tip T of the convex heat portion reached the adjacent layer S.

With this seal, nodular resin pools 9 to 12 as shown in FIG. 3 were formed at both ends of the boundary between the seal portion and the non-seal portion.

When the lid of the sealed container was opened, the cutting of the sealing layer 6 and the peeling between layers at points A and B were performed extremely smoothly, and the peel strength (JIS K6854) was 800 g / 15 mm.
The cutting strength was 1000 g / 15 mm, indicating good easy-opening characteristics.

For comparison, when the lid was opened for a sealed container having a resin reservoir portion formed by sealing under a press-fitting condition in which the tip T of the convex heat portion did not reach the adjacent layer surface S, the seal layer at points A and B, particularly point B was obtained. Was not cut smoothly. That is, in this case, the peel strength is 800 g / 15 mm,
Although excellent in easy-openability, the phenomenon that the sealing layer 6 continues to be peeled even after the point B has occurred, and even when cut and opened, the sealing layer 6 is separated from the adjacent layer 8 and is unsightly in appearance. Was something.

〔The invention's effect〕

Since the safety and easy-openness of a seal in a sealed container are mutually exclusive performances, it has been difficult to achieve both in the conventional sealing method.However, according to the sealing structure of the present invention, the sealing interface and peeling Is performed, the smooth peeling is provided without being affected by the sealing strength. Furthermore, since the sealing layer is very easily cut and opened by the action of the large resin reservoir, the perfect sealing performance and easy open performance are always ensured.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a sealing step for producing an easily-openable sealed container of the present invention, FIG. 2 is a cross-sectional view showing a sealing point, and FIG. 3 shows a sealing state and a state of a resin pool. It is an expanded sectional view. FIG. 4 is a cross-sectional view showing the direction of the force required to open the seal portion, and FIG. 5 is a cross-sectional view showing the state at the time of opening. DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Lid material, 3 ... Flange part 4 ... Convex heat part, 5 ... Seal board 6 ... Seal layer, 7 ... Seal layer of lid material 8 ... Adjacent layer 9, 10, 11, 12, 13, 14: Resin pool A, B: Cut portion of seal layer S: Adjacent layer surface, T: Tip of convex heat portion X: Force.

Claims (1)

(57) [Claims] (1) a lamination strength between a seal layer and an adjacent layer opposed thereto is 300 to 2000 g / 25 mm, and a thickness of the seal layer is 10 to 7
The sealing strength of the container flange portion and the lid material, which is 0μ, is not less than the lamination strength using a convex sealer, and the sealing layer and the adjacent layer at both ends of the boundary between the sealing portion and the non-sealing portion are formed of resin. A method for producing an easily-openable hermetically sealed container, which comprises press-fitting a tip of a convex heat portion at least until reaching a layer surface adjacent to a container flange portion in a sealing method for forming a knob-shaped resin reservoir.