JP2739994B2 - Manufacturing method of 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 performed in the past is to appropriately control the sealing strength with the 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 sealing conditions, environmental temperature, adhesion of contents, etc.
Frequent fluctuations occur. If the variation is biased toward the weak side, there is a danger of leaking of the seal. On the other hand, if the variation is biased toward the strong side, the peeling property is deteriorated and the opening becomes difficult.
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 solve 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) has been attempted. Does not break well,
There is a drawback that the contents are difficult to remove.

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, 63-25).
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, strict control is required for the position setting at the time of sealing. There is the above problem. 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.

JP-A-63-307073 discloses an easy-opening method in which the multilayer peel strength is made smaller than the heat seal strength, and a concave seal layer is formed on the inner end of the heat seal portion of the multilayer material by pressing through another resin material layer. A flexible package and a method for producing the same have been proposed. This structure eliminates the necessity of strictly setting the position of the seal plate.However, when the heat pressure condition is increased due to the simultaneous formation of the heat seal portion and the concave seal layer, the resin constituting the seal layer wraps the innermost layer. In this case, the initial peelability is reduced.

In addition, a method has been developed by the present applicant for sealing such that a resin pool is formed by a resin constituting a sealing layer and a resin constituting an adjacent layer on both sides of a boundary surface between a flange portion and a non-sealing portion having a specific property (see Japanese Patent Application No. Sho. 63-216227).

[Problems to be solved by the invention]

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 interfacial separation between the seal layer of the main body and the lid material seal layer, both seal layers undergo complicated plastic deformation in the sealing process, so the pressure resistance is improved, but it is difficult to recede in terms of easy openability. there were.

Although the above-mentioned prior invention greatly improved the problem relating to the easy-open property, there is still room for improvement.

The present inventor has conducted various studies on the improvement points, and as a result, it has been found that forming the resin pool of the constituent resin of the sealing layer and the adjacent layer only at the boundary between the sealing portion and the non-sealing portion on the container side further improves the openability. It has been proved that it is effective to increase the height, and it has been confirmed that it is advantageous to apply a sealing plate having an inclined surface as a means for forming the resin pool.

A method of sealing using a sealing disk having an inclined surface is also disclosed in Japanese Patent Publication No. 57-7975, but when such a pressure fluctuation is applied, the sealing strength at the innermost end of the seal is extremely high. In some cases, easy openness may be reduced.

The present invention solves this drawback by using a container flange portion having a specific property and other elements, and provides a method for manufacturing a sealed container having an easy-open performance.

[Means for solving the problem]

That is, the method for manufacturing a sealed container provided by the present invention is characterized in that the laminate strength of the seal layer and the adjacent layer facing the seal layer is 300 to 2000 g / mm, and the thickness and thickness of the seal layer are 10 to 70 μm. In sealing the material, the inner peripheral edge is located at the flange portion by using a sealing disk having an inclined surface (3) of 15 ° from the inner peripheral edge to the outer peripheral edge with respect to the flange surface. So that the sealing strength to be formed is equal to or higher than the lamination strength, and at the boundary between the sealing portion and the non-sealing portion on the container side, a bump-like resin pool is formed by the constituent resin of the sealing layer and the adjacent layer of the container. The configuration is characterized in that heat sealing is performed from the top of the lid material in a state.

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 sheet layer and the adjacent layer of 300 to 2000 g / 25 mm (peeling angle 180 °, peeling speed 200m
m / min measurement), and 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 the sheet layer thickness is 1
If it is less than 0μ, sufficient sealing properties cannot be ensured.On the other hand, if the laminating strength exceeds 2000g / 25mm and the thickness of the sheet layer exceeds 70μ, the sealing strength becomes extremely high. This is because the strength increases and easy openness 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 manufacturing process of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing a sealing step, in which a lid member 2 is placed on a flange portion 3 of a container 1 and heat-sealed using a sealing plate 5 having an inclined surface 4.

The inclined surface 4 of the sealing disk 5 is set at an angle (θ) of 3 to 15 ° from the inner peripheral edge to the outer peripheral edge with respect to the flange surface as shown in FIG. If the angle of the inclined surface is less than 3 °, it is difficult to form the resin pool and the cutting and opening of the seal layer at the time of peeling does not proceed smoothly. On the other hand, if the angle exceeds 15 °, the edge becomes an acute angle and the lid becomes sharp. There is a risk of cutting the material 2 and none of the objects of the present invention can be achieved. Further, it is desirable that the width of the sealing plate 5 be designed to be half or more of the width of the flange portion 3.

When sealing, the inner peripheral edge portion E of the sealing disc 5
Set so that is located on the flange part 3 (see Fig. 2)
The sealing strength to be formed is equal to or higher than the laminating strength, and under the heat and pressure conditions at which a nodular resin pool formed by the constituent resin of the sealing layer and the adjacent layer of the container is formed at the boundary between the sealing portion and the non-sealing portion on the container side. Heat sealing is performed from the top of the lid material 2.

FIG. 3 is a cross-sectional view showing the state of the flange portion 3 heat-sealed as described above. The flange surface is fused on the entire surface where the seal plate 5 contacts, but the inclined surface 4
, The degree of pressurization increases toward the inner peripheral edge, and reaches a maximum below the edge portion E. For this reason, the resin component constituting the sealing layer 6 and the adjacent layer 8 of the container 1 is pushed out from the lower part of the edge portion E where the pressure is the strongest toward the container side, and the bulge bulges at the boundary between the sealing portion and the non-sealing portion. Forming resin reservoirs 9 and 10 are formed. At this time, the resin layer 11 is formed along with the sealing layer 7 of the lid member 2.

In the seal portion, the lid 2 and the container 1 are completely fused, 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 the resins. In this state, the sealing strength is higher than the lamination strength of the sealing layer and the adjacent layer of the container.

(Operation)

In the sealed container manufactured by the method of the present invention as described above, there is no danger of leaking the seal because the container body and the lid member are completely fused by the action of heat and pressure.

At the time of opening, a force X as shown in FIG. 4 is applied to the lid member 2, and first, the peeling starts smoothly between the sealing layer 6 and the adjacent layer 9 of the container 1. This peeling continues to the resin pooling portion, but in the process up to this stage, the force X functions to peel off between the sealing layer 6 and the adjacent layer 8 of the container. Then, when reaching point A, the force X acts on both sides of the peeling and the cutting of the seal layer 6 so far, but the distribution of the force X is dominant in tearing the seal layer 6 due to the presence of the resin puddle projecting like a knob. Becomes

Through the peeling and cutting action described above, finally the fifth
It is easily opened in the state shown in the figure.

〔Example〕

High-density polyethylene (HDPE) with an overall thickness of 850μ, seal layer density 0.955, melt index (MI) 5g / 10min, and polypropylene with melt index (MI) 0.5g / 10min for the adjacent layer (also serving as outer layer) (PP) 2
The layer seal was made by coextrusion. Then, this sheet was vacuum formed, the inner diameter was 70 mm, the outer diameter of the flange was 82 mm, and the height was 30.
mm container body was obtained. The flange thickness of this container body is 80
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 member made of 25μ / HDPE60μ was overlaid, and heat-sealed at a temperature of 180 ° C and a pressure of 10kg / cm ² using a sealing plate with a seal width of 8mm and a different slope from the inner peripheral edge to the outer peripheral edge with respect to the flange surface.

The table below shows the state of the flange portion, the opening property of the lid, etc. in comparison with the inclination angle (θ) of the sealing plate using the sealing container manufactured in this manner.

[Effects of the Invention] Since the safety and easy-openness of a seal in a sealed container are mutually contradictory performances, it has been difficult to achieve both in the conventional sealing method, but according to the present invention, the interface for performing the sealing is used. And the interface at which the peeling is performed, it is possible to peel without being influenced by the seal strength. Therefore, even if the safety of the seal is sufficiently performed, the ease of the peeling is not impaired, and the perfect sealing performance and the easy-open performance are guaranteed.

Moreover, if the sealing method of the present invention is adopted, the pressure at the outer peripheral portion of the flange becomes relatively small, so that the initial peel is good and the cutting of the seal layer at the point A is smoothly performed. A sealed container having excellent opening performance can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing a heat sealing step of the present invention, FIG. 2 is a partially enlarged sectional view showing a state of a sealing plate and a flange surface at the time of sealing, and FIG. It is the elements on larger scale which showed the state of the flange part after sealing. FIG. 4 is a schematic sectional view showing the direction of the force required for opening, and FIG.
The figure is a partially enlarged sectional view showing a state at the time of opening. DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Lid material, 3 ... Flange part 4 ... Sloped surface, 5 ... Sealing board, 6 ... Seal layer 7 ... Seal layer of lid material, 8 ... Adjacent layer 9, 10 , 11… resin pool, A… cutting part E… edge part, 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
In sealing the flange portion and the lid material of the container having a diameter of 0 μm, the inner peripheral edge of the inner peripheral edge is formed by using a sealing disk having an inclined surface (θ) of 3 to 15 ° from the inner peripheral edge toward the outer peripheral edge with respect to the flange surface. The edge portion is set so as to be located at the flange portion, and the formed seal strength is equal to or greater than the lamination strength, and at the boundary between the seal portion and the non-seal portion on the container side, the sealing resin of the container and the constituent resin of the adjacent layer are used. A method for producing a hermetically sealed container, comprising heat-sealing from the upper portion of a lid material so as to form a knob-shaped resin reservoir.