JPH03226405A - Manufacture of sealed container with inner lid - Google Patents

Abstract

PURPOSE:To obtain a container which can be sealed stably with high pressure resistance and opened easily by placing an inner lid having a thickness of more than a prescribed value on a container flange part which has a smooth sealing layer, and treating ultrasonic sealing from upward by means of a projected horn with numerous minute projections. CONSTITUTION:A container body 1 consists of a multilayer sheet including a sealing layer 4 and at least its conforming adjacent layer 5. The multilayer sheet should have a laminate strength of 300-2,000g/25mm between the sealing layer 4 and the adjacent layer 5, and further the sealing layer 4 should have a thickness of 10-70mu. An inner lid 3 having a thickness of more than 0.25mm is used as a lid member. It is desirable that film which forms the inner lid 3 should have a sealant layer 6 of material to attach intimately with the sealing layer 4 of the container flange part 2, and it is most preferable that the sealant layer 6 and sealing layer 4 should be made of the same resin. The sealing process consists of placing the inner lid 3 on the container flange part 2 having a smooth sealing layer 4, and treating ultrasonic sealing from upward by means of a projected horn 7 with numerous minute projections.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is composed of a plastic cup body having a flange portion and a thick drop lid, and provides easy-opening properties and packability of the lid material. The present invention relates to a method for manufacturing a sealed container with a drop-lid.

[Prior Art] Plastic sealed containers with easy-to-open lids are widely used as containers for packaging various foods.

The most common easy-open structure that has been in practical use has been developed by changing the composition of the resin that makes up the sealing layer of the lid to maintain the sealing strength with the container flange within an appropriate range (usually 500 to 1500 g/min). 15 am), and the sealed interface is opened by beer (interfacial peeling type).

However, with this interfacial peeling type, the seal strength provided is easily affected by sealing conditions, environmental temperature, adhesion of contents, etc., so it is difficult to control the desired range, and it is often difficult to control the desired range. There are drawbacks to it. When this variation is biased toward the weak side, seal leakage occurs, and conversely, when it biases toward the strong side, it impairs beer quality and impairs ease of opening.

In particular, seal leakage is a fatal defect in a sealed container, so a measure is usually taken to set the heat and pressure conditions of the seal to be high, even at the expense of beer quality.

In order to improve these problems, for example,
As described in Japanese Patent No. 37597, there is a known method of opening the container by delamination between the sealing layer on the side of the container and the layer adjacent thereto (delamination type). However, when attempting to adopt this structure using a normal sealing method, there is a problem in that the sealing layer portion does not break smoothly, making it difficult to remove the contents. In this case, in order to separate the release layer and the adjacent layer into a container, a structure in which a cut is provided in the flange part (Japanese Patent Laid-Open No. 61251363, No. 63-7
No. 8, No. 63-25037, etc.), the flange has a cutout to start peeling and a cutout to stop peeling! Although a number of improvement proposals have been made including a structure (Japanese Patent Application Laid-open No. 63-96060), there is a risk that the pressure resistance will be impaired in these structures. Furthermore, if the seal position is not properly controlled, the seal portion becomes difficult to cut, and there are cases where the lid and the container body cannot be separated, and problems remain in terms of unsealability.

On the other hand, if the lid material of the container is made to have a certain thickness and is formed into a drop-lid shape, it can be provided with a shape-retaining property that allows refilling after opening, which is convenient for preserving the contents. However, with the conventional sealing means using heat and pressure, it is impossible to seal when the thickness of the lid material exceeds 0.25+ am, so it is virtually impossible to expect the lid material to retain its shape after beer. Met.

[Issues to be solved by the invention] As a result of repeated research into achieving both pressure-resistant sealing properties and easy-to-beer properties in containers using thick drop-lids, the inventors found that in the sealing process, numerous strong and weak portions were created on the surface of the release layer. When the drop lid is ultrasonically sealed with a dotted distribution, a seal structure is created that allows for smooth opening by peeling between the eyebrows without impairing the sealing performance even if the thickness of the lid material used exceeds 0°25 am. We confirmed the facts that can be formed.

The present invention was developed based on the above-mentioned knowledge, and its purpose is to provide a sealed drop-lid container that has a drop-lid with good shape retention, maintains stable pressure resistance, and can be opened smoothly and easily. The point is that it provides a manufacturing method.

[Means to solve the problem]

In order to achieve the above object, the method for manufacturing a sealed container with a drop lid according to the present invention is a container in which the lamination strength of the seal layer and the adjacent layer facing it is 300 to 2000 g/25--, and the thickness of the seal layer is 10 to 70 μm. In a method of forming a sealed container by sealing a flange part and a lid material with a sealing strength exceeding the lamination strength, in the sealing step, a drop lid having a thickness of 0.25 mm or more is attached to a container flange part having a smooth sealing layer. The first constituent feature is to superimpose the two parts on top of each other and perform ultrasonic sealing from the top using a protruding horn having numerous microscopic protrusions.

The second component is that the sealing process requires a thickness of 0°251
A drop lid of 1 Im or more is placed on the container flange, which has numerous minute recesses formed on the whole or part of the circumferential surface of the sealing layer.
It is characterized by ultrasonic sealing from the top using a flat horn.

Hereinafter, the present invention will be explained in detail along with the drawings.

FIG. 1 is a sectional view showing a drop-lid sealed container to be manufactured according to the present invention, where l is a container body formed into a predetermined shape by vacuum forming, for example, 2 is a container flange portion, and 3 is a flange portion 2. It is a glued lid.

The container body 1 is made of a multilayer sheet having at least a sealing layer 4 and an adjacent layer 5 facing thereto.

The material composition of the multilayer sheet may be, for example, a simple two-layer sheet in which the sealing layer 4 is made of polyethylene resin and the adjacent layer 5 is made of polypropylene resin. It is also possible to form a six-layer sheet in which a barrier layer of a compound or polyvinylidene chloride resin, an adhesive layer, and an outermost layer of polypropylene are laminated. In some cases, the outer layer or intermediate layer of a multilayer sheet may be laminated with other materials such as metal, paper, or ceramics.

These multilayer sheets constituting the container body 1 have a sealing layer 4
The laminate strength between and adjacent 115 is 300 to 2000
g/25II11 (peeling angle 180°, peeling speed 200
mm/min, at the time of measurement), and the thickness of the sealing layer 4 is I
It is required that it be in the range of θ to 70μ. The reason for this is that if the lamination strength is less than 300g/25aua and the sheet layer thickness is less than 10μ, sufficient sealing performance cannot be secured;
This is because if the thickness exceeds 00g/25n+m and the sort thickness exceeds 70μ, the peeling resistance upon opening will increase, impairing the smooth beer quality.

A drop M3 formed to a thickness of 0.25 m+m or more is provided as the lid material. It is desirable that the film for forming the drop lid 3 has a sealant layer 6 made of a material that tightly adheres to the seal layer 4 of the container flange portion 2. In the most preferred embodiment, the sealant layer 6 of the lid material is made of a material that tightly adheres to the seal layer 4 of the container flange portion 2. They should be made of the same resin material. The film may be a single layer, but it can be formed into a multilayer structure combining aluminum foil or plastic materials with good barrier properties to improve shape retention.

In the sealing according to the present invention, the thickness of the container flange portion 2 is 0.
The sealing strength of the container flange portion sealing layer 4 and the adjacent layer 5 is increased by stacking drop-lids 3 of 25 m or more and using ultrasonic sealing means.
This is done by sealing to a state where the strength is higher than that of the laminated material, and it is not possible to form a hermetic seal with sealing means other than ultrasonic sealing.

The sealing process has the above-mentioned two configuration modes, and one of these methods is adopted.

As shown in FIG. 2, a drop lid 3 is stacked on a container flange 2 having a smooth sealing layer 4, and a protruding horn 7 having numerous microscopic protrusions is applied from the top for ultrasonic sealing. This is the process of

If the number of minute protrusions of the protruding horn 7 is too small, it will not contribute to the ease of opening the package, and if it is too large, it will significantly weaken the laminate layer, so it is desirable to set the number of minute protrusions at about 50 to 500/car''.

The cross section of the container flange formed by this sealing process has a shape as shown in FIG. The parts appear. The stress concentration areas that appear are scattered in countless numbers on the surface of the peeling layer, and the s! function.

In the second configuration, as shown in FIG. 4, a drop lid 3 is stacked on a container flange portion 2 in which countless minute recesses 8 are formed on the sealing layer 4 surface, and ultrasonic sealing is performed from above using a flat horn 9. It is a process. The minute recesses 8 formed in this case are formed on the entire surface of the sealing layer 4 as shown in FIGS. 4 and 5, or on a part of the circumferential surface as shown in FIG.

Formation of the minute recesses 8 can be carried out by, for example, ultrasonic treatment, hot or cold pressing, a method using high frequency, etc. However, in order to form a homogeneous and accurate minute recess over the entire flange portion, It is preferable to apply ultrasonic treatment using a fine protruding horn. Minute recess 8 to be formed
The number is 1CI11! The number is preferably in the range of 50 to 500 pieces.

This is because if the number is less than 50 pieces/C11", the effect of improving the opening performance is weak, and if it exceeds 500 pieces/C2, processing becomes difficult.

As shown in FIG. 7, the cross section of the container flange formed by the above sealing process is an integral piece in which the sealant layer 6 of the drop lid 3 and the seal layer 4 of the flange 2 are firmly adhered and filled in the minute recess 8. However, due to the presence of minute recesses, a region A with a high degree of stress concentration and a region B with a weak stress concentration appear on the surface of the peeling layer, and this strength distribution leads to relaxation of resistance during peeling.

[For production]

According to the present invention, by utilizing ultrasonic treatment as a sealing means, it is possible to firmly seal a drop lid having a thickness of 0.25 m or more to a container flange.

Therefore, it becomes easy to seal the container with a thick lid with good shape retention, which was impossible with conventional heat-sealing techniques, and the container is given the function of a container with a lid that can be repacked after opening.

The seal structure that is formed is that the sealant layer of the drop lid and the seal layer of the container flange work together to form a strong adhesive layer that is stronger than the laminate strength of the peeling layer surface, so it has stable pressure resistance against internal and external pressure when sealed. At the same time, in the sealing process according to the first and second configuration aspects, a seal structure in which stress concentration sites are continuously and countlessly scattered on the release layer surface is formed, so through the action of the unique interfacial strength distribution, The resistance to peeling is skillfully reduced, and smooth opening with a good beer feeling is always achieved. When the material is arched upward, peeling starts between the adjacent layer 5 of the container flange portion and the uniform sealing layer 4, but due to the effect of the interfacial strength distribution of continuously scattered A and B, the thick lid material Despite this, smooth peeling progresses, and eventually the thin seal layer portion (part 0) intervening in the innermost layer of the flange portion is destroyed and separated, resulting in a complete opening.

These effects work together to produce a drop-lid sealed container that has both stable pressure-resistant sealing properties and excellent easy-to-open properties and can be packed.

〔Example] The present invention will be explained below based on examples.

The thickness of the entire example is 850μ, and the material of the sealing layer has a density of 0.9.
55, melt index (Ml) 5g/10ml
n, high-density polyethylene (HDPE), the adjacent layer (also serves as the outer layer) has a melt index (old) of 0.5 g/s
A two-layer sheet made of polypropylene (PP) was prepared by coextrusion. Next, this sheet was vacuum formed to have an inner diameter of 65III and an outer diameter of the container flange of 75II11.
, a container body with a height of 251111 was obtained. The thickness of the sealing layer of this container body was 20μ, and the lamination strength between the sealing layer and the adjacent layer was 1500g/25-rin.

Next, the number of protrusions on the seal layer surface of the container flange was 256.
Ultrasonic treatment was performed by applying an ultrasonic horn with micro-protrusions of 1/cm" to form countless micro-concavities in the entire area.The conditions for the ultrasonic treatment were an output of 2KW (energy used: 2KW).
25 J), a pressing force of 338 KPa, and a time of 0°3 seconds.

As a lid material, a 0.5 mm thick sheet made by dry laminating stretched nylon to a sealant layer of polyethylene (thickness 20 .mu.m), which is the same as the sealing layer of the container, was used and formed into a drop lid shape.

A sealant layer of a drop-lid was superimposed on the sealing layer surface of the container flange, and ultrasonic sealing was performed using a flat horn under conditions of a pressure of 450 KPa and a time of 0.3 seconds to produce a sealed container with a drop-lid of the present invention.

When the lids were opened for the 50 sealed containers obtained, all of the containers opened and separated smoothly until the end with a beer taste without resistance, and the condition of the opened surface was good with no phenomena such as fuzzing or deformation. Met.

In addition, there is an adhesive rubber plate (thickness 1.5 mg) in the center of the drop lid.
+) and measured the bank pressure when the needle was inserted and air was injected at a rate of 2 cc/sec, the average puncture pressure was 0.9 kg/c2, and the range of variation was 0. 2
kg/cm", showing stable and good pressure resistance performance.

For comparison, when the above sealing process was performed by heat sealing, the sheet layer of the container flange portion and the sealant layer of the drop lid could not be bonded together.

〔Effect of the invention〕

As described above, according to the present invention, by adopting a unique sealing process using ultrasonic waves, a thick drop lid with good shape retention is used to maintain stable pressure-tight sealing properties while ensuring smooth beer flow. It becomes possible to manufacture a sealed container whose lid can be easily opened.

Therefore, since the drop lid can be repacked once opened, it is extremely useful as a sealed container for packaging and preserving all kinds of foods.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a drop-lid sealed container to be manufactured by the present invention, Fig. 2 is an explanatory view showing a sealing process according to the first configuration aspect, and Fig. 3 is a sealing according to the sealing process according to the first configuration aspect. An enlarged sectional view of the flange part showing the state, Figure 4 is the second configuration! An explanatory diagram showing the sealing process by Mr. S, Figures 5 and 6 are partial plane views showing the flange part according to the second configuration, and Part 7 shows the seal obtained in the sealing process of the second configuration. It is an enlarged sectional view of a flange part showing a state and an unsealed state. 1... Container body 3... Drop lid 5... Adjacent layer 7... Protruding horn 9... Flat horn 2... Flange portion 4... Seal layer 6... Sealant layer 8 ...Minute recess

Claims (1)

[Claims] 1. A seal that exceeds the lamination strength between a container flange portion and a lid material in which the seal layer and the adjacent layer facing it have a lamination strength of 300 to 2000 g/25 mm, and the thickness of the seal layer is 10 to 70 μm. In a method of forming a sealed container by strongly sealing, a drop lid with a thickness of 0.25 mm or more is stacked on a container flange having a smooth sealing layer, and a protruding horn with numerous microscopic protrusions is used from the top. A method for manufacturing a sealed container with a drop-lid, characterized by ultrasonic sealing. 2. A drop-lid with a thickness of 0.25 mm or more is placed on the container flange portion in which numerous minute recesses are formed on the whole or part of the circumferential surface of the sealing layer, and ultrasonic sealing is carried out using a flat horn from above. A method of manufacturing the described drop-lid sealed container.